Bl. G. / 11.0 gr means it's proofed for an 11 gram lead bullet, (Blei Geschoss). To convert from grams to grains avoirdpois, use a factor of 15.43 hence 170 grains.
The crowned G proof mark means Gezogen, (rifled barrel). The Crown over U is a definative proof / inspection mark. I can make the other crowned mark out in the picture.
The 7,6mm / 46 might well be a 8.15x46,1/2mm as this was a common target round. In that case the 7,6mm must be the lands diameter. Dropping an 8.15x46, 1/2mm round into the chamber to check for fit is a quick way to narrow down your search. If it doesn't fit then you know you have more work to do. If it does, don't assume too much, (and don't just shoot it), without doing a cerrosafe chamber cast to confirm if this is the correct round for this rifle.
The 3.30 is perhaps the date of proof, March, 1930. JP Sauer were making a very similar rifle, also known as a "Tell", between 1896 and 1936.
It looks like the word "N" appears on the receiver, in which case it's nitro proofed. It would still pay to get a good gunsmith to check it out before use.
