Hi,
Very nice grenades MT-LB!
Your Koweshnikow fuze are rare production, but it's nothing unusual in this fuze.
I have seen this fuze fitted with F-1 body French type, but with Soviet also...
Here's some of mine... not so nice condition like yours, becouse all was find on battlefields from 1945 in Poland.
On second pics, some Russian manufacture stamps on fuzes - for now unfortunately unknown for me.
As you can see, there was two kind of UZRG fuzes; open on top, and closed (pics.3).
Unfortunately all of mine ww2 F-1 with Koweshnikow fuzes are in the our local museum for while...
Best regards.