Proof Marks, Codes, Calibre Conversions & Evaluations

Correctly identifying your antique pistol and knowing its provenance/lineage, maker and history is essential for maintaining quality records and improving the value of each piece. For quick reference, the links below will take you to several sources for proof mark identification (except the United States, which did not proof pistols), US martial inspection initials (cartouche), a handy  metric to calibre conversion table, bullet chart and list of ammunition calibres no longer commercially available. A search online will also yield several British and European book titles dealing with proof marks, which are worthy of your collection. To assess the value of your antique pistols or to understand evaluation descriptions, we have listed the two main methods below to assist you


US Military Small Arms Inspectors Cartouche Initials

UK/European barrel proof marks

Gunmakers Codes & Markings; Colt Serial Numbers

Convert Millimetre to Calibre

Bullet Charts

Calibres No Longer Commercially Available


Two common methods are used to evaluate antique firearms, as follows:-

  1. NRA Condition Standards: Modern guns are classified as new, excellent, very good, good, or fair. Antique guns are classified as excellent, fine, very good, good, fair, or poor.
    • New: All original parts, 100 percent original finish and in perfect condition.
    • Excellent: All original parts, over 80 percent of its original finish with sharp lettering, numerals, and design on metal and unmarred wood.
    • Fine: All original parts, over 30 percent of the original finish in tact.
    • Very Good: All original parts, 30 percent or less of the original finish in tact.
    • Good: Some minor replacement parts are present. There may be rust or light pits and it’s in good working order.
    • Fair: Some of the major parts are replaced and may need additional replacements on minor parts. Metal is rusted and there may be light pitting all over. It’s in fair working order or can be easily repaired to be in working order.
    • Poor: Both major and minor parts are replaced and it still needs major replacement parts and extensive restoration. The metal is deeply pitted and it’s generally undesired as a collector’s item.
  1. Percentage System: This method rates the percent of original finish that remains on the gun with a range of 0 – 100 percent.