The gun appears to be in great condition, with matching numbers, including the magazine (which is very rare and adds to the value)
It appears to be a Mauser Banner, Police variant, but I couldn't see the proofmarks and acceptance stamps clearly enough to be sure. And in determining which specific variant, the markings are critical.
IF it is the model I suspect, the standard catalog of Luger (2003) lists a VG specimen at $2,250. Excellent @ $3000. I don't know what the going price would be today, sorry.
Very nice pistol, if you do get it, I would recommend not shooting it. Its in great shape, all matching including the mag, that makes it a "primo" collector's piece.
Shooting it will not harm the collector's value, in this case, as there are no, "unfired" Lugers from this era. However, I still would recommend against shooting it, because, a single broken part can turn a $3000 Luger into a $1500 Luger instantly. Or worse. Breakage of minor parts isn't common, but the guns are getting old, and stuff does happen. Even if it is a non ser# part, a replacement means the gun is no longer completely original, and its value drops, radically.
There are Luger forums, experts there should be able to do a better job identifying it, and giving you a current value. Good Luck!
I can tell you that while we have no idea of where the gun actually was carried, that Luger was not made for military use. Guns made under contract for military sale have an S/42 marking on the toggle. (a code, not a date)