Mystery Frame

[Alain]

Dear Gentlemen,

I appeal to your expertise in submitting to your scrutiny a misterious frame with strange features:

- added grip safety with mounting block and enlarged slot.

- safety lever frame area slightly milled (on entire area) down as if to erase a marking.

- stock lug absent BUT enough excess metal to machine it. There is a big round smooth bump where a stock lug is normally located.

It came with a mix of Simson and Navy parts. Could it be a an added grip safety Simson commercial?

Frame is numbered 43220, but it seems to me to have been originally "322", as numbers "4" and "0" are very slightly misaligned compared with
the other numbers.
It also has a horizontal C/N proof on left frame rail.

Thanks a lot in advance for your help.

Alain Capel

Paris France