It was made by whoever was the low bidder at the time. Spiratone brand gear was all contracted out that way. Most of the stuff was decent quality, but I wouldn't call any of it first rate. I owned some Spiratone gear in the late 60's. A good friend owned one of their lenses, it wasn't all that great. If memory serves, it was a 400mm M-42 mount. Several of us in our club tried it out, none were impressed.I will commend the darkroom gear they put out, that all worked very well indeed, as did alot of the general camera accessories. Your zoom may have been built by Asanuma, they were one of the first companies to make zooms.