Trying to understand what I'm seen from this 1897 shotgun:



I think there are original Birmingham Proofs from 1897 -1904
13 bore - 12/c - right barrel cylinder; left barrel choke

I think it was reproofed on London 1954-1989.
.728" - 2 1/2" chamber - 3 tons

But what are the other two marks?
"Crown over R" - Liège? I though "R" was for rifle.
"LP over 87" - ????

And this is the water table / action flats. First mark is Birmingham proof. Is the other Crown over CP?

The original proof was 1887-1896 - there is no 1896-1904 oz. max.
The reproof (Crowned R) was by the London Proof House in 1987; at 3 TONS = a service pressure of 8,960 psi by Burrard's conversion from LUP
It is Crown over GP = Gunmakers Proof for the London Proof House.

Thanks Dr. Drew....I see it now. And the "LP over 87"?

london proof in 1987

Excellent - I Learned stuff tonight and there is more to this request than meets the eye. Thanks.

Some may be confused by the 1987 proof and "tons" marks. Shouldn't that have been bars? Per Christopher Austyn's book "Modern Sporting Guns", p. 81: " . . . there was a brief period (1985-89) when either Imperial or metric marks could be chosen . . . "

A much better reference is Nigel Brown's. He was a Proof Master after all! On page 266 of his London Gumakers book, he explains that Bar was not introduced until 1989. Also the imperial proof marks that could be requested from 1984 to 1989 used the Tons SERVICE pressure while the metric version used the Kg PROOF pressure.

Toby;

It is good that you brought up the name of Nigel Brown. His three books on London, Birmingham, Scot, and other gunmakers of the UK is a Must Have in the library of a serious student of British guns. The charts included in Vol 3 are worth the price of the book alone.

Thanks much for the explanation, Toby. It looks as if, during that transitional period, our British cousins were doing their best to confuse those of us on the other side of the Pond. We'd had time to grow accustomed to a service pressure proofmark, only to see a transition to a proof pressure mark. Although I expect the latter might have something to do with all the other CIP countries using proof pressure marks.

Back 20 years ago, when I was working on an article for Shooting Sportsman magazine, we sent the article in draft to Roger Hancox for his comments. His reply clarified another area of confusion re the interpretation of the bars marks:

"The article mentions that at the time of SAAMI's creation, pressures were measured with crushers. And when later they began using transducers they discovered that readings were different and designated crusher readings as LUP (lead units of pressure). The same applies to the CIP but unlike SAAMI they still call the crusher values bar!"

He then went on to explain that the standard CIP pressure values of 650 bar service pressure and 850 bar proof pressure have equivalent transducer values of 740 bar service and 960 bar proof. Prior to that explanation, I was attempting to convert from bar values to psi values by multiplying by 14.5, which obviously produced the wrong results. We're still stuck using psi values on this side of the Pond . . . once again demonstrating that the Americans and the British are, indeed, two peoples divided by a common language.

The CIP site confirms that 850 BAR = 12,328 PSI by crushers (LUP) is actually 960 BAR = 13,924 PSI by transducers (13% higher), and adds MPa to the confusion
“These cartridges, if they are to be fired from standard proof shotguns (ie those proved to 960 bar [13,924 psi transducer] or, previously, 850 bar [crusher]), or magnum proof shotguns (ie those proved to 1370 bar [19,870 psi transducer] or, previously, 1200 bar [crusher]) must not exceed the maximum admissible service pressure of 74 MPa (new units “megapascals”, in place of the old 740 bar) specified by the CIP and measured by means of a piezo-electric transducer.”