Home / Proof Marks / Birmingham — crown over BNP

Birmingham — crown over BNP

British proof marks · 1954 to today.
What it looks like
A crown with the letters BNP beneath it.
Where it is on the gun
Barrel flats and breech.
Date range
1954 to today.

What it tells you

What this mark authorises you to say

Birmingham Nitro Proof. This is the modern British definitive proof mark and the one you are most likely to find on a gun still in use: any British shotgun sold today must carry valid proof, and if the barrels have been altered, the chambers lengthened or chokes added, it must be reproved before it can lawfully be sold.

What it does not tell you

What this mark does NOT say

It says the gun was proved, on a date you have to find elsewhere. It does not make the gun safe with every modern cartridge, and it becomes invalid the moment the barrels are materially altered.

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.

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 lookup

Other 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.