I have an SPI 60mm f/20 that is a clone of the Astro R-61, it carries the diamond-OTC mark, yet I believe we are just about certain that these were made by Astro. So the mark may be that of the exporter and have not as much to do with the factory that made the scope, as we usually think.
Correct. Many exporters appear to have their specific marks on binoculars and telescopes as well. Other markings represent the actual shop that assembled the bino or scopes in our case.
Going thru the archives of "The Comprehensive List of Japanese Symbols" thread, many believed that the mfg or distributor symbol on the 1960/61 and up Swifts is "A V A". Instead I now believe that "A M A" is the correct abbreviation which would stand for the "Associated Manufacturers Agency".
With respect to Swift 1960 or 1961 on up telescopes that do not have the infinity symbol on the name tag. I found this information listed several places on the following website of miniature binoculars.com pertaining to what the three letters and or symbol actually represents on the focuser name tags.
"Japan based Associated Manufacturers Agency located at Nakano 6-22-10 Nakano ku, Tokyo, Japan is a Japanese trading company and/or importer and exporter. Believed active from around 1958 to the present, it is listed in Japanese business directories as specializing in “Optical Instruments and Lenses”.
Associated Manufacturers Agency, Exporter Brands: Swift. Manufacturers observed of Swift brand binoculars of this type.
This is information I've come across trying to research the distribution/exporter origins of the older pre 1960 Swift & Anderson telescopes using the site looking for correlations of Swift bino mfgs/distributors.
I have a couple 1958/59 Swift & Anderson No. 819 models that have the diamond <TJK> stamped on the bottom of the pinion block. It is an distributor company in Japan also found on early Swift binos. Also on late 50s Swift & Anderson No. 820 60mm x 800mm, the pinion blocks look to have a decal of diamond <TJK> symbol as well.
See info pics on the <TJK> symbol.