doublegunshop.com - home Forums General Discussion DoubleGun BBS @ doublegunshop.com Proof marks interpretation?

I need help with the interpretation of these proof marks. Which ones are the newest ones? In fact I know that the newest ones should be the ones expressed in international units, like "bar" for pressure and metric system for bore diameter, but I still need your opinion.
Thank you anticipately.
I do have another question to ask once I understand which marks to consider currently valid.

Looks like the pattern welded(?) tubes experienced at least 4(with the most recent lighted pic) sets of proof with the first possibly being Bohemian with the right tube at 16.3mm and the left tube at 16.4mm(might be Belgian?). 16.3mm and 16.4mm seem out of the 20 bore range or are just on the edge. Are there any marks forward of the flats?(Answered by the lighted pic). Then a set of London proofs which most have been worn off. Then the "Crown" over "BP" with "shot" for Birmingham 1904-1925 and "Crown" over "BNP" with "950 BAR" Birmingham 1989-2005. A better pic of the crossed scepters adjacent to the "crown" over "R" will probably yield a data. A puzzle I must say.

Kind Regards,

Raimey
rse

The gun is a 20 ga Army&Navy. I thought that the 16.3 and 16.4 marks would represent the bore diam. in mm and would be the newest proofs along with the "20X70" over "950 bar". THe barrels measure .636 RB and .639 LB which is less than the 16.3mm=0.641" and 16.4mm=0.645".
The marks on the barrels in front of the flats are "20B" and "not for ball" and "M" on both barrels.

With the decimal centered between the numbers and minus the "mm" stamp the "16.3" & "16.4" looks Bohemian. But someone will come along and set the record straight. There must have been a repair at some point.

Kind Regards,

Raimey
rse

Raimey;
Do you take the .626 & .637 as bore dias from a later proof? Certainly seems inconsistent with an earlier proof @ 16.3 (.642")& 16.4 (.646"). I am in agreement with your interprtation though, just doesn't look right that it could have been proofed at a later date & the bores be smaller. Do you have any ideas as to what occured here?

My take on this is:
There is one set of black powder proof marks pre 1887, hence the
20B ?M Not For ball etc.
The next set is the decimal bore size,2 1/2" 65 grs. Black Powder
7/8 Shot etc. which is post 1955 but pre -metric.
The last set is the metric which looks to me like 16.3 on both barrels, 70MM or 2 3/4" chambers, and 950 Bar nitro Proof.

I don't remember how to convert the BAR Nitro Proof stamp into shot shell pressure. Does the Bar Nitro Proof marked at 850 or 950 mean a low pressure vintage type load (like RST's) in the 5,000 to 6,000 range or a higher pressure modern load in the 9,000 to 10,000 range?

Sharpsrifle, 1 bar is 14.5 psi, thus 950 bar is 13,775 psi.

Terry, my take on it is the same. I don't know if I am right or just hopeful. If this is right what I don't understand is that the bores measure 5 thou below the 1989 proof marks at 9" from breech.