cable,
Your drilling was made by someone in or around Suhl for marketing by Halang and Bachner. It was proofed between early 1893( when the 1891 Proof Law came into force) and 1911(when improvements were made that changed some markings). The 16 in a circle means it had standard 16 gauge chambers, which would be 65mm( 2 1/2-2 9/16"), not the 70mm ( 2 3/4" that is used now). The 17/1 is the bore diameter of the shot barrel, ahead of the chamber, as expressed in gauge measurement. This works out to be about 16.64mm (about .656"), which is a little tight but not too unusual. The crown G means that barrel was proofed to fire a single projectile( bullet). The crown U means it passed a "View proof" which is a detailed inspection, including verification of dimensions, performed after firing a definitive proof, using the provisional proof load. A crown S is the mark for proof to use shot in that barrel, but the font of this on your drilling seems to be different. The 62/78 is the bore( not groove or bullet) diameter, as expressed in gauge measurement. This works out to about 10.67mm( .419"), which precludes the 45-70. A chamber cast will be necessary to identify the nominal cartridge it is chambered for. At the time you make the chamber cast, also "slug the barrel", or capture enough of the barrel to get a good ID of the groove diameter. There are also some markings that seem to be cruder that the proof house marks. This may very well be the designation of the powder used for proofing. It seems like a "P", an "M/71", and some I can't make out. This may be some reference to the powder used in the M 1871 Rifle ammunition. This powder is usually shown as NGP M/71( new rifle powder m/71). Note that either way, the drilling is proofed for black powder. BTW, the shot barrels are "Damascus", but the rifle barrel is steel( likely from schilling forge-note the "s" in an ellipse). Raimey may come in and tell you about Halang und Bachner.
Mike
