Like rgg_7 said, it's a sporting rifle built off of a 98 large ring mauser action. My best guess would be that it's pre-WWII based on what looks to be the nitro proof marks on the top of the bolt handle. My guess is that on the left hand side of the receiver ring, you'll find something like "St. m. G." and below it, some numbers. That could potentially tell you what it was originally chambered for as well, given the lower numbers would indicate the weight of the bullet used. Directly underneath the barrel and in front of the receiver ring is where I would look for the proof marks from Zella Mehlis if this was a commercial barrel/receiver. The thing that throws me off is the hole in the trigger guard, which would indicate that it's a Gewehr 98. Then again, it could just have been a replacement for the original, which could have been broken or damaged. The really neat thing about these old rifles, is that they are a mystery unto themselves, but one thing you can be sure of, is that they were handmade by skilled artisans the like today you'd pay thousands for. The scope mounts are "claw mounts" meaning that the scope can be removed and reattached with very little deviation in zero....again, handmade. Finding rings for it is an expensive venture to say the least. As far as the serial number, those are usually a number designated by the rifle builder himself. I find it highly doubtful that any internet search will provide you with any kind of information regarding age or anything else for that matter. It's possible that the markings on the underside of the barrel can provide you with a general date as to when it was proofed at Zella Mehlis. As far as anything more than that, I'm not an expert, but can only provide you with this one piece of advice: be very careful cleaning it. If you'd ever be interested in selling it, shoot me a message as I collect them. Best of luck.
~Jaeger
