TO bring together most of what has been said here...
You've got an East German Volkspolezie K98k, a nazi manufacture rifle overhauled in East-Germany post-war for the Volkspolezie (peoples police), a sort of East German paramilitary police.
The crossed mosins "X" does indicate russian capture originally. Post war this rifle passed through russian hands and eventually into East Germany.
At that point the rifle was completely overhauled. You'll notice the NAZI eagle and swastika on the receiver are defaced, the numbers on the rifle would have been scrubbed and re-stamped to match the receiver if they didn't match in the first place (you'll notice that your bolt at least has been ground and re-stamped to match, and the floorplate has been restruck to match.)
The barrel also would have been replaceds, and I bet under the stock line you'll see a U over a crown, indicating post war, East-German manufacture. The "K13" and "K9" on the wrist of your stock indicate that it is post war, East-German as well.
The Czech-style front sight guard was also adopted by the East Germans.
Does your rifle have the last two digits of the serial number electro-penciled onto the rear facing part of the bolt?
A very nice rifle, and probably the most professionally done and aesthetically pleasing of the various refurb programs. Definatly makes the Russian refurb program look like a gong show...