It didn't seem appropriate to post these into the usual forum categories because of what they are, With of the magnification and size of these, I'm hesitant to call them binoculars, as they are more like what most people would term to be "opera glasses", but there's none of the extra hardware like they'd have - like, a handle or flip-up end caps - and I'm unaware of what name they would have been sold as, since these came without papers of any kind or a box. There's nothing to pin down a date either, but I would assume from the typeface of the company name that these are probably late '50s to mid 60's. Anyone have any ideas?
All I know for sure is that they work well, they really are singly coated optics, and are extremely easy to break down for a thorough cleaning with very little effort. A lens spanner and a standard drafting compass is all that's needed for tools to do the job.
Thanks for the page link PF. That was a great start for info.
I did find out that the 'JB' number on the top arm is the manufacturers code, and it turns out that this model wasn't made by Yashica itself, but by Subaru Kogaku Kikai Co. Ltd., who also made similar models under several other brand names.
If anyone is looking for a cross reference, there's a listing of the 200+ Japanese binocular manufacturers at this link. It turns out that although these don't have any extra hardware or features, they are still considered to be useful as 'opera', or arena, or live theater glasses, or any indoor settings where modest magnification and a wider field of view work better than standard field glasses would.
I also did a trademark search at the US trade and patent office on the "Yashica" trade name that specifically uses the same type face, and it was first applied for on March 3, 1959, and was registered and approved on March 27, 1962. It was effective until it was cancelled on April 1, 2016. Not too helpful as a way to pin down production dates overall, but at least it offers a starting date.
I'll keep looking, but there's not much data on the now-defunct Subaru Kogaku Kikai Co. Ltd., and the newer field glasses (the 7x and 8x versions) that might have been made by Yashica don't seem to use any JB numbers at all - even though they were required to.