Need help to identify this .22 conversion

[Joe359]

Hello all,
Great forum and my first post here... I'm wondering if anyone has seen or knows anything about this .22 conversion unit. Looks like a gunsmith has soldered the .22 barrel unit inside the original luger barrel to make it a permanent conversion. What puzzles me is the HEP - NYC on the top (gunsmith? conversion unit maker?) - anyone have a clue to what that refers to? The conversion unit parts are serial numbered to themselves except the magazine which is nazi marked and serial numbered to another gun. It's a great little shooter but was interested to see what I can find out about its history...

Thanks,
Joe