It has the Swiss Luger style front grip strap (absolutely straight) unlike the American Eagle (1900, 1906, 1923..)and the Military P08 styles that have the slight finger rest curve at the extreme bottom of the front strap/

I don't remember that the Interarms Lugers paid extreme attention to original Luger Model/Contract/Year details. But I'd guess it is one of their 'Swiss' versions, the first style made.
They didn't sell well (seems like they were $300 back then in the early 70's). The style was the big reason,,everyone wanted a 'German Luger' and if they were going to pay that kind of $$ for one it had better look like one, and be n 9mm.
The first run Swiss style had 6" bbls and were 30cal. They then made them in 4" 9mm. I think they ended up making them in both calibers and bbl lengths.
The P08 style wasn't a big seller either,,same complaint of too expensive,,after all you could still find and buy a near pristine 'real one' with a holster generally for about the same money.
Then the complaints of jamming started, real or imagined. Hey,,it's a luger after all!.

Interarms called them 'Parabellums',,couldn't use 'Luger' as explained above. Stoeger still owns the Luger trade mark name in N/A.
Those Stainless Lugers made in Texas some years later sported the Luger name after Stoeger bought into the company making them (Aimco), but those are gone now too.
They got a bad rap for QC though some were fine. Mostly investment casting used there.
Those Texas/Aimco/Stoeger made guns sometimes get confused with the Mauser/Interarms venture.
Two entirely different tries at resurrecting the Luger.