Proof Marks



Rules of Proof

Rules, Regulations and Scales of Proof, a schedule to the Proof Act, are the working instructions of the two Proof Houses. The Rules specify the pressure to be used in proof, standards of view and the marks to be impressed on guns which pass proof, together with such detail as bore and chamber dimensions, proof and service pressures.

The latest Rules of Proof, those of 1989, were approved by the Secretary of State, to come into force on 1st November 1989. However, proof under earlier Rules of 1875, 1887, 1896, 1904, 1916, 1925, 1954 and 1986 remain valid provided that the barrel or action has not been materially weakened or altered so that it no longer conforms with that proof mark.

Foreign proof marks

Prior to June 1980, there was reciprocal agreement for recognition of certain foreign proof marks, by international accord. At that time the United Kingdom became a signatory member of the International Proof Commission (C.I.P.), Secretariat, at the Belgian Proof House, Liege. Since then the United Kingdom has recognised all the proof marks of the other member nations and, reciprocally, they all recognise UK marks. The C.I.P. has been working since 1914 for the standardisation of proof, which also involves standardisation of pressure measurements, of chamber and bore sizes and cartridge dimensions.

Currently its members are:

  • Austria
  • Belgium
  • Chile
  • Finland
  • France
  • Germany
  • Hungary
  • Italy
  • Russia
  • Spain
  • United Kingdom

Previous reciprocal agreement continues with the Republic of Ireland as it is not a member of the C.I.P.

It should be borne in mind that all countries have made changes in their proof marks from time to time and it is not practical to include within these pages all the proof marks that have been used over many years.

It should also be observed that proof in France was optional until 1960 and there have been marks impressed by some French gunmakers, which appear to the layman, to be official proof marks, but are not.

Additionally there were proof marks used in Austria, Germany and Italy which were valid in this country before and up to the outbreak of World War Two, but which are now invalid and have been replaced by new marks. Care must be taken in differentiating between the old unacceptable marks, and the newer valid type.

A book containing all the currently valid, foreign and UK proof marks, is available at a small charge from the London and Birmingham Proof Houses.

In general the importation of foreign arms, bearing no proof marks or bearing marks not now recognised is an offence, unless those arms are submitted to a Proof House within 28 days of arrival. The sale of such guns unproved would constitute a further offence. This warning applies particularly to arms made in countries where there are no official Proof Houses.


Black Powder Guns

Many shotguns proved under Proof Rules before 1904, when the nitro proof marks were introduced, and some shotguns proved before 1925, when nitro proof became compulsory, were proved only for use with black powder.

Such guns will not bear any of the nitro proof marks. It should be clearly understood that, whilst such guns may be proved for black powder, they are unlikely to be legally proved and must be deemed unsuitable for use with present day cartridges, until they pass a nitro proof test.

Types of proof

There are two main types of proof:

  • Provisional proof in general applies only to shotgun barrels in an early stage of manufacture and is designed to prevent the maker continuing work on defective tubes.
  • Definitive proof applies to all arms and is effected either in the "white" or in the finished state.


Additionally there is a special proof to cover loads developing pressures in excess of normal service loads. This can be either as a voluntary proof, to satisfy a particular requirement, or as a compulsory proof where the arms are designed for unusually heavy loads.


Proof for steel shot

In 1993 a C.I.P. specification was adopted covering special proof for guns which can be used with steel shot. The specification lays down shot size and hardness, the number of proof rounds to be fired through each barrel and the pressure to be generated at 25mm and 162mm. A special "Steel Shot" proof mark will be stamped on each barrel of such weapons that have successfully been proved.