Leopold died in 1870 but his company continued to manufacture barrels.
There are pre-WW I doubles with the LB mark and also Whitworth steel marks. It is not known if a Belgian barrel maker acquired the Leopold Bernard trademark after the company ceased operation in 1890 but it appears likely. There were a number of Liege "Bernards"
https://docs.google.com/document/d/1fMs-Mn60ei9QsRcHT5Urm_eHobzJnaDKZiP3FP0fXb0/edit?tab=t.0 More information here
http://www.doublegunshop.com/forums/ubbthreads.php?ubb=showflat&Number=313605&page=1 The gun dates to 1910-1921 (I don't see a
lettre annale and it's probably pre-WWI) but there should be a chamber gauge mark within a diamond on the flats
Ted is correct. 17.2 mm = .677" = 15 gauge. The L barrel muzzle constriction is 16.2 = .638" so choke is .039"
The marks closest to the breech may be the maker's mark
The pre-1924 16g standard service load was about 1 oz. with 2 3/4 Dram Eq. (1220 fps). Loads of that period ran about 8500 psi
After 1924 the max. service pressure was 600 kg/cm2 = 8534 psi
+ 10 - 14% by piezoelectric transducer measurement
I can say with confidence that the barrels were of quality fluid steel; likely by Cockerill and likely Siemens - Martin open hearth process. Pre-WWI Siemens were similar to AISI 1021 - 1034 Carbon Steels. I've analyzed a sample of Pieper Eclipse “Hercules Compressed Steel” (Pieper only used Cockerill) and it was non-standard 1030 with a tensile strength of almost 100,000 psi
Manufacture d’Armes à Feu Liégeoise and
Fabrique-Nationale-Herstal also used Cockerill steel. At some point Krupp must have licensed
Cockerill Sambre, as Fluss Stahl Krupp Essen marked tubes stamped with “Acier Cockerill” have been documented.
Please post high resolution close up images of every mark on the barrels and flats when you get the gun.