This is 9mm, no date, blank toggle, SN 4355e. The take down, safeties, trigger, bottom of the sideplate and left grip are numbered 55. No numbers on any other parts. The bore is pristine. It has been restored by Thor.
According to Costanzo, the proofs on the right receiver, WaA66=1933 Simson military proof, and DE H=1933 Simson Heres acceptance mark.
The SE 823 on the bottom of the bbl are "independent manufacturers code" for suppliers of bbls. The 8 is the month (August) and the 23 is the year.
The breech block has two DE6=Simson 1923-25 military parts proofs; the middle toggle has a Crown lazy N and the rear toggle has SE Jt3. I couldn't find this exact mark in Costanzo, but found a similar one that indicated a 1928 Army depot proof.
I believe this gun to be a 1933 Simson rework using a conglomeration of parts. Would appreciate any corrections or comments to help in identifying it.