This lens is the one you can see most commonly on the Zenit 19.
Zenitar-M 1.7 / 50mm
Zenitar-M 1.7/50mm, provided by par Alexey with the Zenit 19 received on may 22nd, 2009.
Tests: Please note that these tests were made with the means at hand, not in a "scientific" way. See here.
On the edges we get the same as a Helios 44. But in the center it is much better for large openings. It would have been a good candidate to replace it, perhaps more expensive to make?