Thanks a lot for Delcour-Dupont explanation.
What does the number 17796 on bottom rib indicate?
There is a stamping JA under left barrel. It is on extreme right corner of the 3rd pic. I have seen this same stamping on another Jeffery and that Jeffery was stamped Fred Williams on both sides of receiver. What does it indicate?
Raimey is correct. The barrels were sourced from Delcour-Dupont. During this period Delcour-Dupont was a large supplier of barrels, both fluid and damascus, to the trade. This was just prior to a huge upheaval in Belgian wages, which adversely affected their gun trade.
The number on the under rib is most likely just a factory job number. The JA marking as Raimey suggests, is an internal reference from the factory. It most likely represents the tradesman who did the final striking of the barrels in Birmingham.
By the way, Herakles is the Greek name that we know as Hercules (the Roman version of the name). Yet another marketing term.
Pete
