Odd thingie on Zorki 3M

Hi all!
I am proud owner of Zenit TTL, 122, Fotosniper 12, Lubitel 166 Universal and 2 LOMO LC-A. :)
Recently I expanded my collection with Zorki 3M. It is a bit different from what I have seen. The difference is small socket(?) under time knob. I will open it at the weekend, but meantime I have question:
Have any one of you seen something like this? Do you have any clue what that might be?
Previous owner states that he don't know what that thing is and that he got it like that. He also have Zorki 3 with the same thing.
S/N: 5515444

Photos were taken by previous owner. I can take some more tomorrow.

Hi Mateusz, welcome to the forum!

Seems like a home-made flash sync socket modification, it's quite common on soviet cameras.

Best regards,
Vlad.

I thought so, but I haven't seen that type of socket yet.

quote:

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Originally posted by Vlad

Hi Mateusz, welcome to the forum!

Seems like a home-made flash sync socket modification, it's quite common on soviet cameras.

Best regards,
Vlad.

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You were right. Do you know name of this type of socket?
Here's proof: