Certainly an attractive camera (per nice photos). Engraving is somewhat different than your average non-export Zorki (the "Z" is smaller?) and more like the Zorki.Zorkis, only the small Z- Zopkuu is, as mentioned, engraved at a 45º angle. The speed dial looks slightly smaller than mine and the avg. Zorki.Zorki in the pics; more the size of my Leica.IIIs. My Zorki.b also has the same shutter spring. The "Made in USSR" on the back and that ser.# are certainly a kicker.
Maybe rare (can't say I've seen one before) maybe a [factory] proto - can't say there either. And I'm really not sure how he knows it's one. Would anyone fake, cobble, or improvise an Export Zorki.1? There are plenty of legits to be had. But a proto? they might? Saying it's "the only one known" and "there's no record in any collector books" makes you wonder..."hmmmm... Soooo, where did you get the camera and where did YOU get YOUR information?"
I read somewhere that there were plenty of [rare] custom cameras out there. "Custom" as in, someone bought a handful of Zorkis and took them to a jeweler/camera tech/neighbor with engraving tools and had them personalized/altered/customized. There are some [rare] Yuri Gagarin comemoritive Zorkis around, but are they State commissioned factory made or ...? They all seem to be slightly different, so no one is quite sure. 😕
Legit proto or not, it's a nice looking camera and Zorki.1s shoot just fine. Need one? Hey, why not?
edit w/chuckle:The other item he has listed is described as, "ZENIT SNIPER GUN - ONLY ONE PIECE KNOW TO EXIST !!!! ULTRA RARE! NO DESCRIPTION OF THIS ITEM CAN BE FOUND..." Gotta admit, this guy is on a roll! 😀