Hello All! Herr Doktor,
did You try mounting it on a movie-camera ...?
(I fear You do not own it, though; only, We may stay at the website's photos. Is is so?).
I must say, at first it works out the same impressions like with Daan.
But I strongly think, it is a genuine Olympus objectiv from FTL serie: both newer OM System and older FTL made 50mm/1,4 and both which marked as "G.ZUIKO - AUTO-S" (OM 50/1,8 says "F.ZUIKO") and both NOT Macro; but its barrel is of FTL one. _
Mounting it on a 8mm or 16mm movie-camera, it became! a Tele-photo by different film-frame size (like mounting a 35mm lens on a not full-frame Digital Camera). _
Should be verified if it does focusing according with the distances printed on the focusing-ring; if so, it means that mysterious mount is well calculated in its length and then a Tele-photo focusing from cm.40 (1.3 ft.) may already be well called as a macro lens. _
If tube-mount lengthens, objectiv can focusing nearest; but We may take the best quality, on the first case.
The 1" screw mount is properly a standard mount for movie-lenses. Also, don't forget many movie-cameras were made as Reflex, too; then, easily allowed to take macro films.
I do not think it as a home-made lens; I think it a limited production, yet based on an Olympus FTL 35mm Lens 42x1 (Praktica) screw thread mount Model and modified into a 1" screw mount version for movie-cameras.
You might make further research among web.sites regarding cine/movie equipments.
Thanks for reading, Greetings from ITALY!