I was contemplating a purchase of 'father' of this lens, silver Zeiss Tessar 50/3.5 for SLR on M42 thread, with some fancy coating, but in the end that money went elsewhere. After all, it would never be my daily shooter lens and 70$ is a fair amount of money out here.
Zenit looks like a concrete block compared to any post-1972 Japanese camera and I quite frankly am accustomed to lightweight, ergonomic and functional cameras from four islands in Asia. However, their stock optics, normal 50 mm lenses with f/1.8 are somewhat dull. Yes they are sharp, yes they are good performers (some of them - great performers actually), but they all lack character and sometimes I want some beautiful rendering instead of clinically sharp images. And that's where M42 comes in. Tessar scheme specifically. Of course I use Flektogon and Biotar b*stards from Russia as well, but Tessar has some punch.