I'm trying to find information on a rifle I have. It is a single shot, .22 cal., checkered walnut stocked with a forward sling stud. The rear stud is missing. Open iron sights, receiver is grooved, barrel is also grooved so the rear sight can be adjusted for distance from the shooting eye, 25 1/2" barrel with the following on it: Sportmodell Walther (in a banner) then Meisterbuchse. On the receiver it has Waffenfabrik Walther and on a line below that, Zella-Mehlis Thuringen. All this in German lettering. So the story goes it was brought back from the war by a GI who took it out of a shot up German Staff car. It's barrel has some blue missing that looks like it could have had some blood on it. I'm wondering when it was made, how many, model, value, any information would be appricated. Thanks.