It looks like a 106 variant of some description. The serial dates it to around 1937/1938 but I wouldn't expect to see a balance without screws from that date. I haven't seen all of the 106 variants but I have never seen one with a plain balance, nor that regulator and the balance cock is a slightly different shape from the ones I have seen. Does it have a seconds sub-dial or is it a central seconds movement? - they made both in the 106.
It is subsecond one Maybe it just a shot while on the move :/ But in that case there should be some blured circle around the wheel
I think this is the cal. wich 106 with the extension B: cam disc regulator as referenced at bidfun. I also think the balance wheel is original- i also have a couple of watches of the same cal. and period with exact the same BW(plain). Yours is very clean wich is rare.
The balance wheel does have screws - you can see them blurred. I think the balance wheel is coming to a stop in one direction, giving the impression that it's not moving. Not sure why the hairspring isn't blurred as much...