−27%
Palmetto State Armory
Glock 19 Gen5 MOS
$549.99
$399.99
View at retailer
Birmingham — crown over NP
British proof marks · 1904-1954.
What it looks like
A crown with the letters NP beneath it.
Where it is on the gun
Barrel flats.
Date range
1904-1954.
What it tells you
What this mark authorises you to say
Definitive nitro (smokeless) powder proof, in use from 1904 until BNP replaced it in 1954. Its presence is the fastest way to place a Birmingham-proofed gun on the right side of the smokeless-powder transition.
What it does not tell you
What this mark does NOT say
It does not tell you the year within that fifty-year window, and it does not mean the gun was made in 1904 or later — only proved then. A reproofed gun will carry the later mark.
Sources for this page
Every claim above is attributed. The class of source is shown with each one, because a national proof house and an anonymous forum table are not the same evidence — and on proof marks the difference matters.
-
British proof marks, London and Birmingham
collectorAn established specialist archive or collectors' society.
Reading marks to identify and date a gun
Proof marks name the test and the era. The serial number, where a maker published a browsable chart, can name the year. The lookup cites the threshold behind every result.
Open the serial number lookupOther british proof marks
Mark descriptions observed and verified 2026-10-14. Proof marks are stamped by hand on guns up to a century old; a photographed stamp and a description in a book are not the same evidence. If a mark on your gun does not match anything here, that is a real answer — see the notes on unidentified marks.