rook2c4 wrote:
I agree, they are close-up filters. I have a few of them as well, picked up at a flea market a few years ago. Samyang has been making lenses, filters and other related accessories under the Star-D brand name all the way up through the 1990's, and perhaps later. I've never encountered Star-D products dating before the 1960's, but I won't rule out the possibility that they do exist.