great collecable lens indeed, congratulations! It's written:
Experimental Zavod VOOMP Leningrad "Kimar" (???) F=21 cm 1:4 No. 2 1935. I'm not sure about "Kimar" engravings only, and I'm too lazy right now to check my lens books. May be someone will correct me?
An early VOOMP lens, probably for large format camera and not necessarily Russian. The name sounds like it may even have been made for a cine or movie camera. Similar to this one:
this lens is for wooden large format camera 13X18. the camera is not typical russian, other bellow and smaller than a fk-camera. the camera has no name-plate and has a stamped serialnumber in wooden. english or french camera. it`s very similar to your "aviar".