Quality Control

Custom Coin Spec Sheet: Line-by-Line Buyer Guide

Why coin quotes go wrong

Most custom coin problems start before tooling. The buyer sends a loose concept, the factory fills gaps with its own assumptions, and the first sample comes back visually close but commercially wrong. A challenge coin is controlled by measurable inputs: diameter, thickness, relief height, edge geometry, base metal, plating stack, color fill, and packaging. If two suppliers receive the same vague brief, they may quote different processes, and the finished coins can differ in weight, tactile feel, edge crispness, and cost by more than the buyer expects.

The hidden cost is rework. Changing thickness from 2.5 mm to 3.5 mm can move a coin into a different die setup, change press load, and shift unit price by roughly USD 0.18 to 0.75 depending on size, finish, and order volume. Switching from a plain edge to a rope, reeded, or diamond-cut edge can add another USD 0.10 to 0.60 per piece. If the artwork also needs deeper relief or secondary polishing, sample timing can slip by 3 to 7 days. That is why a coin RFQ should read like an engineering note, not an art brief.

A clean spec also shortens lead time. Once the factory has exact dimensions and artwork, sampling usually takes 7 to 12 days, production 15 to 25 days, and shipping time depends on the lane. A missing tolerance or unclear finish often adds time because the supplier has to redraw, re-confirm, or cut a new sample tool. The safest quoting process is to lock the numbers first and discuss aesthetics second.

Core dimensions and tolerances

Start with the three dimensions that drive nearly everything else: diameter, thickness, and relief depth. Common promotional coins are 38 to 45 mm for pocketable lapel-style pieces, 50 mm for standard presentation coins, and 60 to 70 mm for ceremonial or collector pieces. Thickness usually sits between 2.0 and 4.0 mm. Below 2.0 mm, the coin can feel thin and may flex slightly; above 4.0 mm, weight rises quickly and packaging, postage, and die load all increase.

Relief depth matters just as much as overall thickness. For clean 2D or low-relief work, raised and recessed areas are often 0.3 to 0.6 mm apart. For more sculpted coins, 0.8 to 1.2 mm is common, but that requires tighter polish control so lettering does not lose legibility. A practical rule is simple: the more text and fine linework you have, the less aggressive the relief should be. If the smallest text height is below 1.2 mm, keep the relief shallow and avoid deep shadow cuts.

Do not leave tolerances implied. For die-struck coins, a sensible outer diameter tolerance is ±0.2 mm for pieces under 45 mm and ±0.3 to ±0.5 mm for larger coins. Thickness is commonly held to ±0.15 to ±0.25 mm, depending on alloy and process. If the coin must fit a capsule, presentation box, or display slot, the case dimension should be confirmed first, then the coin spec should be set to fit that cavity with at least 0.2 mm of clearance on diameter. For post-plating dimensions, ask whether the quoted tolerance is pre-plate or final measured size.

Lock one master spec for reorder stability. That spec should include nominal diameter, nominal thickness, permitted tolerance band, target weight if the buyer cares about hand feel, and the approved edge profile. Without that control sheet, later batches tend to drift because different factories interpret the original artwork differently.

Spec line	Typical range	Buyer note
Diameter	38-70 mm	Use 38-45 mm for wearable or pocket coins; 50 mm for standard presentation
Thickness	2.0-4.0 mm	Stay at 2.5-3.2 mm unless you need a heavier ceremonial feel
Relief depth	0.3-1.2 mm	Shallow for text-heavy coins; deeper for sculpted artwork
Diameter tolerance	±0.2 to ±0.5 mm	Confirm capsule or box fit before quoting
Thickness tolerance	±0.15 to ±0.25 mm	Tighter control is easier on struck brass than on cast zinc

Build method and edge style

The build method determines both appearance and predictability. Die-struck or stamped coins give the sharpest transition lines and are usually the best option for logos, crests, seals, and text that must stay crisp. Cast coins are better when the design has deep 3D forms, irregular silhouettes, or a sculptural front face, but they usually show softer edges and a little more variation in polish. If the buyer wants razor-sharp lettering, a complex sculpted relief is the wrong place to save cost.

The common manufacturing split is brass for struck work and zinc alloy for cast work. Brass handles detail well, takes plating cleanly, and usually gives the best premium feel. Zinc alloy supports more complex shapes at a lower entry price, especially on larger coins, but the surface can read softer if the mold or polish is not controlled tightly. Iron can be cost-effective in some stamped programs, but it is less forgiving on premium finishes and is not the first choice for high-detail presentation coins.

Edge style is one of the most under-specified items in an RFQ. Flat, bevel, reeded, rope, spur, and diamond-cut edges all change machining time and visual weight. A simple flat or bevel edge is often the best default for event coins because they stack cleanly and keep cost stable. Rope and reeded edges suit heritage, military, or commemorative themes, but they can add USD 0.10 to 0.60 per coin and may extend lead time by 2 to 4 days on complex orders. Deep diamond-cut edges usually need stricter polish control because they show tooling marks more easily.

If the coin will be carried in pockets or handed out at events, avoid edges that are too sharp or too aggressively textured. They can snag fabric, wear faster, and make the coin feel less comfortable in the hand. The buyer should define whether the edge is purely decorative, intended for grip, or required to fit a display mount.

Build choice	Best for	Avoid when
Die-struck brass	Sharp text, crests, premium feel	Deep sculpted 3D shapes
Cast zinc alloy	3D artwork, irregular silhouettes	Razor-sharp lettering
Flat/bevel edge	Budget control, stacking, clean handling	When the edge must be a design feature
Rope/reeded edge	Military, heritage, premium presentation	Very tight cost targets
Diamond-cut edge	Bright sparkle, limited-edition look	Mass reorders with simple artwork

Metal and plating

Base metal changes structure, finish behavior, and reorder consistency. Brass is usually preferred for high-detail coins because it machines well and plates evenly. Zinc alloy is often used for lower-cost pieces or designs that need casting flexibility. The buyer should ask for the base metal to be named explicitly in the quotation, because a low quote may be based on zinc when the buyer assumed brass. For premium coins, request the alloy family, nominal thickness, and whether the surface is polished before plating or after plating.

Plating should be stated by color and, when possible, by thickness target. Decorative coin plating commonly runs around 0.1 to 0.3 microns for flash-type cosmetic work and around 0.5 to 1.0 micron for more durable decorative finishes, though capability depends on the line, base alloy, and surface prep. Common finishes include polished gold, antique gold, polished nickel, antique silver, black nickel, copper, and dual-plating combinations. Antique finishes are useful when recessed text must stay readable after polishing. If the buyer wants a long-wearing retail coin, ask whether the coating is sealed with lacquer, wax, or oil and whether that seal is included in the quote.

Do not overuse dark finishes on tiny text. Black nickel, dark antique silver, and deep gunmetal can look strong on a render but lose contrast when the relief is shallow or the lettering is under 0.35 mm wide. If the coin must survive frequent handling, ask the factory whether it applies clear lacquer, protective oil, or wax. Those coatings can reduce tarnish, but they may also mute antique contrast and alter the surface feel. For humid storage or long transit, ask for salt-spray or storage-aging expectations in days rather than general promises.

For long shelf life or humid climates, ask whether the plating is sealed and how it behaves after 6 to 12 months in storage. A finish that looks right on sample day may change slightly if it is not protected, especially on copper and silver tones. The right question is not only what color you want, but how the finish should age.

Finish	Typical use	Practical caution
Polished gold	Premium corporate coins	Shows fingerprints if unsealed
Antique gold	Heritage or military themes	Needs enough recess depth to read well
Polished nickel	Clean modern look	Can look flat on low-relief artwork
Black nickel	High-contrast modern styling	Small text can disappear
Copper	Warm commemorative tone	Tarnish control matters in storage

Color fill and surface texture

Color fill should be specified by process and visual intent. Soft enamel gives a tactile, recessed look because the color sits below the metal line. Hard enamel is leveled down and polished smooth, which usually reads more premium and is better for coins that will be handled often. For a coin program, the buyer should decide early whether the piece should feel textured and dimensional or smooth and presentation-grade. If the coin has very fine seals or lettering, hard enamel can preserve cleaner edges, while soft enamel can emphasize contrast at lower cost.

For production safety, line widths should usually be at least 0.35 mm on the main artwork, with 0.25 to 0.30 mm being the practical floor only for simple separation lines. The smallest fill islands should also be checked; tiny isolated color spots often fill poorly or chip during polishing. Recess depth for enamel is typically 0.2 to 0.4 mm, and very fine boundaries need enough wall height to keep colors from bleeding together. A useful buyer rule is to keep the minimum gap between adjacent colors at 0.2 mm unless the factory has already approved the layout.

Texture can be specified as well. A sandblasted background creates contrast, brushed fields add movement, and matte surfaces reduce glare. Polished raised elements against a matte or blasted background are the safest choice when the artwork includes logos, seals, or commemorative text because the contrast stays legible at different angles. If you want a premium retail look, ask for one texture per field rather than mixing too many finishes on a small coin.

• Confirm Pantone references for each fill color, not just a screen image.
• State whether small gaps between colors are acceptable or must be closed.
• Ask for the minimum line width and smallest fill island the factory will accept.
• Specify whether the final face should be glossy, matte, or mixed finish.
• Reject samples where the smallest text loses legibility at arm’s length.

Reverse side and special features

The reverse side should never be treated as leftover space. Some buyers want a mirrored front, while others need a clean reverse with text, numbering, or a polished blank field. Serial numbers, QR codes, and custom backstamps are all possible, but they must be tied to legibility and the chosen production method. A QR code on a small coin only works if the module size, engraving depth, and scan distance are compatible; otherwise it becomes decorative instead of functional. For typical coin sizes under 45 mm, keep QR use conservative and test it before mass production.

If the coin must stand upright, fit in a capsule, or mount into a display, those requirements belong in the spec sheet. A display coin may need a flat reverse and a controlled center of gravity, while a pocket coin may benefit from a slightly heavier edge and a less reflective back. If you want a backstamp, state whether it is raised, recessed, or laser-engraved, because each option affects tooling, cost, and lead time. Laser engraving is best for small variable data; recessed backstamps are better when the back needs to match the front visually.

Special features should also be written as measurable requirements. For example, if the coin includes numbering, define whether the number is sequential, where it sits, and the minimum character height. If the coin includes a magnet, define the magnet size, pull strength, and polarity. That level of detail prevents the factory from substituting a visually similar but functionally weaker solution. If the coin is meant for a commemorative set, also define whether the reverse must match a companion piece in diameter and edge style.

Feature	Spec it this way	Why it matters
Serial number	Character height, location, sequence	Keeps numbering readable and consistent
QR code	Module size, scan distance, method	Prevents decorative but nonfunctional codes
Backstamp	Raised, recessed, or laser-engraved	Changes tooling and lead time
Display fit	Capsule or stand dimension	Avoids post-production fit problems
Magnet	Size and pull force	Controls holding strength and cost

Packaging, QC, and approval gates

Packaging is not cosmetic when the coins must survive freight, retail display, or gifting. A clear polybag is the lowest-cost option, but a velvet pouch, rigid box, capsule, or backing card can materially change perceived value and damage rate. Standard carton packing should prevent edge rub and plating scuff. If the coin has a high-polish face, add insert separation so pieces do not contact each other in transit. For direct retail kits, ask for carton-drop protection and moisture control if the route is humid or long.

Quality control should be written as checkpoints, not promises. A practical standard for coin programs is AQL 2.5 for major defects and AQL 4.0 for minor defects, with 100 percent screening for obvious structural faults before packing. Ask the factory to inspect diameter, thickness, plating uniformity, fill overflow, edge burrs, and color match against the approved master sample. For repeat orders, keep one sealed golden sample with measured dimensions and photos. If the order is more than 5,000 pieces, ask whether the factory can provide lot-level inspection records rather than only a summary pass/fail note.

The buyer should define approval gates before production starts. A good sequence is artwork confirmation, 2D proof approval, sample approval, pre-pack inspection, then shipment release. If the order is high value or has a hard launch date, ask for first-article photos within 24 hours of sample completion and in-process photos before final packing. That process is faster than fixing a full shipment after the fact.

QC item	What to inspect	Typical buyer rule
Size	Diameter and thickness	Must match agreed tolerance
Finish	Plating color and uniformity	No patchy tone or visible base bleed
Fill	Overflow, shrinkage, bubbles	No overflow on primary logo areas
Edge	Burrs and sharp spots	No edge that catches cloth or hands
Packing	Scratches and movement	No coin-to-coin contact in transit

Order structure and next steps

The fastest way to avoid a bad coin order is to turn the concept into a numbered specification before asking for quotes. List diameter, thickness, build method, base metal, plating, fill type, edge style, reverse treatment, packaging, tolerance, and acceptance standard on one sheet. Send that sheet with vector artwork and ask each supplier to confirm every line item in writing. If a supplier answers with vague terms such as premium finish, high quality, or standard thickness, ask for numbers before comparing prices.

For a typical MOQ, many factories start around 100 to 300 pieces for simple standard coins, 500 pieces for more complex plated or enamel coins, and 1,000 pieces or more for best pricing on custom tooling. FOB prices vary strongly by size and finish, but a useful planning range is roughly USD 0.80 to 1.80 for simple 38 to 45 mm struck coins at 500 to 1,000 pieces, USD 1.50 to 3.50 for enamel or antique finishes, and USD 3.50 to 8.00 for larger or highly detailed presentation coins. Complex packaging adds more, often USD 0.20 to 1.50 per set depending on box type.

For planning, ask suppliers to quote separately for sample cost, bulk unit price, tooling amortization, and packaging. A sample may cost USD 30 to 120 depending on complexity, while tooling can be waived, refunded, or built into the unit price. If a project is time-sensitive, ask for a realistic schedule in calendar days: proof, sample, approval, production, packing, and dispatch. A clear schedule is easier to manage than a single promised ship date.

If you are buying for a campaign, reprint, or annual program, lock the approved sample as the master reference and store it with photos, measured dimensions, and the exact plating callout. That single step reduces reorder drift more than any decorative option. Once the spec is stable, the factory becomes easier to manage, the quote becomes easier to compare, and the risk of rework drops sharply.

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