The mentioned "rare model"
P 38 pistols would have a
swastika or other
Nazi proof marks as the P 38 served in the
SS along with the
Luger for the better part of
WWII.
One way to find out if your P 38 is one of these highly collectible cruffle waffens is to look at the serial number of the gun and of the magazines, even if it does not have Nazi proof marks as long as the pistol and magazine have the same serial number it is a WWII era P 38 and is highly collectible.
The Nazi proofed specimens command even a higher price as there is a huge demand for Nazi memorabilia out there. And it's not even Nazis who collect these stuff, just WWII buffs and other gun nuts.
Btw, the gun is properly known as P.38, P-38 is an airplane and P38 is a can openner.