Pneumatic self-timer 
Techpribor, Leningrad, USSR
with bakelite case

Partly working. Self-timer fires in appr. 3 seconds (instead of 10-15), most likely the spring is weak. Case is original and has signs of age and use.

Camera "FED-2" is not included and shown as an example of mount.

This is an external pneumatic self-timer which is used for the cameras which are not equipped with built-in self-timer. For your comfort, I took a picture with this self-timer mounted on "FED-2" (which is not included). 

It is screwed in a release button (if it has a carving - for example, early "FED" cameras had a solid release button) or into a special hole. There is a L-cut at the side. Push the switch to the long part and it will fire in approx. 10-15 sec (3 at the self-timer offered) with a pin activating the shutter of the camera.

Inside the self-timer there is a valve. When released this valve takes air via 4 small holes and thus slows the spring. If all the holes are closed the offered self-timer will fire in 5-7 seconds.

Rotating the knob at the top you can increase or decrease the activating time. At the knob there is an inscription "15 seconds" and arrows with + and -. 

Note: pin is pushed from the self-timer very fast! 

Size: 67*18*19 mm
Weight: 27 g (56 g with case)