Fair warning: What I DON'T know about Schuetzen rifles would probably fill a moderate book shelf. I am not any sort of authority. I've seen them at gun shows and had a casual word or two about them.
That IS a schuetzen rifle. It was made specifically for offhand (standing on one's hind legs like a man) slow fire, precision rifle competition. Note the double set triggers, the huge rear sight (to control sun in one's eyes and also act as a blinder to distractions) the curved butt plate to fit into the shoulder and the involved trigger guard also acting as a hand grip.
It seems to be a falling block rifle, with the control lever on the right side. As such, it is nominally a cartridge gun, but not in our modern sense. Schuetzen rifles were originally from the 14th and 15th Century, and muzzle loaders. The rifles accepted technical changes - like brass cartridges - but the sport did not. This rifle most likely uses a rimmed brass case. From the mark on the barrel, the bore diameter is 7.7mm. However, that does not indicate the 7.7 mm Arisaka round. Normally, schuetzen rifles used lead or lead alloy cast bullets; not jacketed. Also, for premium accuracy, bullets were often seated into the rifle bore with a pushing stick or detachable lever device, then the case with charge loaded behind.
To determine the correct shape of cartridge, one would probably have to make a chamber cast and compare that casting to known rounds. Schuetzens did NOT follow conventional norms for cartridges, although the proper case was usually available with too much trouble. In other words, this rifle will most likely NOT chamber and fire the well known 8mm Mauser round. If the chambering is for a regular cartridge, it will be a European cartridge and most likely a black powder round.
If you don't have the current edition of 'Cartridges of the World', this would be an excellent opportunity. Usually one can find something close and informational.
The other marks on the bottom of the barrel are proof marks (the crowns and letters). The other marks (46 1/2) are probably (not guaranteed) pressure levels, but measured in European units - not PSI, CUP, LUP or anything 'ordinary' in U. S. There are probably some marks showing who made the rifle. The 'St' marking may indicate the maker, presuming one knows what it means.
I can see a hint of something on the bottom of the receiver. That may contain a name or something. For all I know, the carving of the rifleman on the butt stock may be the trademark that 'everyone knew' identified the rifle maker.
You now know everything I know. Except I looked on Amazon.com and they have some books on these rifles. You might even luck out with your local library.
Come back and report what you find. Knowledge is cumulative.
They were not intended as hunting rifles, although they would usually shoot a big enough cartridge for up to deer sized critters. It's too heavy to carry very far without a wheelbarrow and a Junior Woodchuck field hernia kit.
