Here's the brief version:
In London...
Barrels were proofed by the Gunmaker's Company, a craft guild with quasi-legal authority that only covered Metropolitan London and (I think) some or all of the County of Middlesex - where London is located.
From some time in the middle of the 18th century to some time at the beginning of the 19th century (we do not have conclusive dates in either case) barrels could be submitted for proof to the Government proof house on Tower Wharf by civilians. Because they were not government property, they were marked with the two strikes of the "crossed scepters" device instead of one strike of that mark along with the "GR & crown" Royal Cypher (which is how government arms were marked). The cost for a proof was 3d, of which the proofmaster kept 1d. From this fund, a banquet was given for the proof house workers each year.
Outside the jurisdiction of the London Gunmaker's Company there was no legal requirement for proof anywhere in Britain until 1813. However, the custom was well established and customers expected to see proof marks so,
In B'ham...
There was at least one Private Proof house which probably began operations around the beginning of the 18th century. As early as 1717 the London gunmakers were complaining that the B'ham marks looked too much like theirs. They were right, as its pretty clear that the private B'ham marks were intended to be easily confused with London marks. The truth is, they regularly are to this day even by experienced collectors. We do not know who owned or operated the private B'ham proof house but the circumstantial evidence comes down strongly on the partnership of Farmer & Galton. These are the common "crowned V' and "crowned P" marks... sometimes seen, quite late, without the crowns, just the letters "V" and "P".
We think... this is still in the conjecture stage... that private proofing on Tower wharf stopped in London around 1804/5. We do not know if it was ever done in B'ham during the Napoleonic wars when there was a "satelite" proof house there.
The new proof house replaced private proof in B'ham in 1813 so all B'ham private marks pre-date 1813 while all B'ham proof house marks are 1813 and later.
The "Ketland proof house" story is attributable to the late H.B.C. Pollard and his 1926 "History of Firearms". Its much too long a story to relate here but I believe I've traced the origins of his honest mistake. The problem is that the story has been repeated ad nauseum for the past 80 years so its deeply entrenched in popular gun lore. This very fine Heylin gun is important to the story because it isn't a B'ham gun and it is much too early to plausibly be attributable to a proof house associated in any way with Thomas Ketland Sr... who was only 31 years old in 1767, had only been in business 7 years and was still in his original location on Litchfield Street.
jp
