"The Broad Arrow", and "The Lee-Enfield Story by Ian Skennerton, afford many specifics of manufacturers' and unit codes and proof marks, and of rifles of Enfield origin respectively. Akin to the longstanding hallmarking system for British silverware, in which letter codes relate to years of manufacture or importation, is an equivalent employed by the British Proof Houses.The problem here is that, unlike silver hallmarking, the Proof House codes were only introduced in 1921 and have been only intermittently applied since then, almost on the whim of the Proof Master incumbent at any particular time. production was proved at Birmingham and the marks should therefore comply with these series.This is nothing new, and proof-house date marks from years past may still not indicate the rifle's date of manufacture. Such a purchase additionally supports such researchers and their work, and is, long term, to the benefit of us all.However, if an estimate of the rifle's age from other sources closely matches the date marks, then you probably have pinned down when it was made within a year or so. The ISBN numbers for these reference books are in the bibliography. When inspecting your rifle and comparing marks with reference sources, be careful not to confuse date marks, or "private view marks", with inspectors marks, which usually carry the factory identification, e.g., "E" for Enfield, under the sovereign's crown, below which is the inspector's identification number; usually two figures such as "39". rifles the Proof mark is only on the barrel (and on the action falling-block), and the third mark on the barrel is the 'NP' mark for Nitro-Proof, also below the crown.
Anschutz target rifles fall into this category, and their system is given on the page for these rifles.
However, we have been made aware, by a contributor, of two contemporary rifles, a BSA Mk.
II Lightweight Martini International and a BSA Century, that each carry what certainly appears to be the letter "I" in the left quadrant (as in Fig. This would suggest that "I" as well as "Q" was no longer deemed to be ambiguous, as had previously been the case with the Fig.1 stamp configuration.
There is therefore an undeniable possibility that year letters after 1958 may each represent dates that should be advanced one year, with "Z" falling in 1975, although this would then conflict with the 1975 commencement of the next series. Conjecture may suggest that perhaps there was even indecision at the Birmingham Proof House, and only a few rifles were stamped with an "I" in 1958 before "J" was substituted, or, a long shot, the 1957 "H" stamps wore out before the end of the year.
We may never know the answer, but can meanwhile entertain ourselves dreaming up such explanations.