Here is a bit of information on Mitchell as i am somewhat familiar of where he s been getting them for years.
Many of Mitchells mausers come from Ex-Yugoslavia successor states where they were sitting in surplus National Guard armories since the early 50s. Yes, The Nazis did take over the production in the 1941-1944 time periods but these guns were made after Tito`s conflict with Stalin in the 1948-1953 tim period.
I ve seen pictures of him purchasing them from the Macedonian Army depots in the early 90s when i lived over there. They have no collector value as he embellishes the story behind them and he s been known to re stamp old guns and surplus guns that were used (most were in storage but some issued during the 90s Yugo Wars). So although he claims this you dont have a guarantee that you ll get a 100% never fired gun as Mitchells refinishes some of them and nowadays most i believe.
As they became obsolete with the SKS being introduced in the 50s because it was a semi and became the standard Yugo Army Rifle until 1972 (AKs started being issued) they still remained in storage and ultimately were sold to Mitchell and surplus dealers for sales in Canada,US and such. They also were used in classrooms for demonstration and learning the gun and disassembly (we had preparatory classes for 2 years to prepare you for mandatory service) as well as going to the range and shooting them when you "Graduate". I was in the last generation of recruits that went through this process training on an M48 and had an SKS issued to me in Basic Training for 3 months.
What you do get is a new shooter grade gun....which you can use and shoot and hunt maybe (a Slovenian acquaintance of mine hunts with it in Alaska).
I have one that i bought from a forum member a few years ago and its an M48.