You have a sporterized K98k that was produced by JP Sauer in 1939. The three "birds" on the receiver are Waffenamts and are proof markings. Your rifle has been heavily modified, buffed, and reblued. It also appears to be in a cut down Gew 98 stock. Its not worth much from a collectors standpoint but if the barrel is in decent shape it should be a good shooter. Here is a photo of my K98k so you can see what it would have looked like originally.