Baikal IZH-?? cal.16/70

I bought this Baikal IZH ?? times ago. The seller ( it was on an auction ) didn’t have much information on this shotgun, too.
So, I am not able to identify the modell, nor I am shure that this gun ia a Baikal and I will be very happy if you can help to solve my „problem“ 😉

What I know about this shotgun:

• serial no. Г5439 ( = G5439 )
• chambered in 16gauge
• extractor
• barrel length 29 3/8″ ( 745mm )
• chokes 17/16, 17/16.5
• branded „Made in CCCP“
• sliding lock, not automatic
• build 1961 ?

some details

The shotgun has a double barrel hook closure / lock and, so far as I can say, an extractor.
Maybe this could be an ejector, too, but the spring is missing ( if there was a spring )

There are also a few markings at the bottom from the barrels, as following

Right barrel

left barrel

Unfortunatly there are no markings at break-down frame, that would be too easy to identify this model 😉
So at least some detailed pictures from this shotgun, which may help for identifying

Baikal IZH-?? detailed pictures

Any help is appreciated, just leave a comment – thank you!