That's an Interarms Mauser Parabellum, since Stoeger owned the Luger name at that time (and still may for all I know).

There's actually quite a bit of information about them in the post-WWII section of the Luger forum:

Pistole Parabellum

The moderator there actually wrote a book I found very entertaining about these guns.

I have one in 9mm and one in .30 cal, they both shoot very well.