The seller lists it as an F1.5 lens- clearly is F2. I have seen ZK lenses like this before. The seller seems to have cut-and-pasted the wrong description, how can they be trusted for a $600 lens.
Same seller:
Find many great new & used options and get the best deals for Zorky BK 1:28 / f 3.5 USSR Rare Wide Angle Rangefinger Lens 000170 at the best online prices at eBay! Free shipping for many products!
www.ebay.com
This one looks wrong. SN engraved in the rear looks too crude, and rear lens cap engraved "Zeiss Ikon"
It looks like a later J-12 engraved to look like a BK lens.
Too many mistakes to take a chance.