"Rhys95," the "J R" stamp you mention is likely that of a Greener's in-house barrel-maker-finisher, and is the sort of identifier that provided a means of quality control over the constituent parts of the gun as it progressed through the stages of manufacture to the gun's final completion. This was a common practice for the historical period, and especially relevant to the productions of outworkers. Such personal identification marks were also stamped into the wooden or metal bits and pieces by in-house workmen for pride of workmanship reasons and as production inspection stamps. Some maker's initials and assorted stamps are avidly sought after by certain collectors, and in some instances can increase the value of the gun substantially.
The initials "J R," serial number "16190," and the "W W G" stamp for W. W. Greener combine to reinforce the suggestion that "16190" is indeed the true serial number that can be attributed to W. W. Greener. These three elements go together and tell their story, to wit: We are the true maker and these our proprietary indicia. Privately labeled guns of the period frequently employed the retailer's proprietary serial numbers. This private label serial numbering would have been a part of the labeling agreement between the actual manufacturer and the retailer requesting the privately labeled product.
I believe that you are correct in surmising that it is illogical for a complete, in-the-white gun made by some manufacturer to the specifications of a private labeler for that privately labeled gun not to evince the serial number of the private labeler along with other private labeling indicators, such as the name of the retailer. Therefore, we continue to believe that "38440" is a serial number series attributable to the retailer, Rosier.
Your alarming description of the condition of the cartridge primers upon firing your gun and the dangerous aftermath is indicative of a very serious problem needing address soonest possible. My guess would be that the problem arises from the firing pins, either they are too long, too sharp, have been nonprofessionally altered, or the pin retracting springs are worn or weakened and in need of replacement. You should cease all live-firing of your gun and take it to a gunsmith who is familiar with antique double guns. This must be done forthwith. Waiting and wondering why could be too costly to your health and irreplaceable body parts. Do not attempt to correct this problem yourself. Instead, please seek professional help, advice and correction immediately!
Regards,
Edwardian
