I made some research about the Meyer Optik Görlitz brand since testers say they even made legendary lenses better (brighter and/or sharper) and because they also produce the Biotar (formerly of Carl Zeiss Jena, who were forced to merge with Meyer and Pentacon in GDR). Their actual owner is OPC, a company for industrial and special optics in Bad Kreuznach. OPC also developes optical products for other companies.
Meyer lenses were produced at OPC's plant since 2018 and are produced in the Meyer buiding of Hamburg since 2021. (so nothing of it is made in Görlitz today) The homepage says all parts are made there, so it should be 100% made in Germany.. Lenses are available for 11 different mounts including M42. Hompage is https://www.meyer-optik-goerlitz.com/
Site can be viewed in English or German
Original message:
Hi,
I found a list of photographic lens makes and who owns them. Often, the country of manufacture is mentioned; otherwise it's a good base for research. It's German but Google Translate gives an understandable Translation. A few brand names get translated, too,

https://www.fotointern.ch/archiv/2021/0 ... re-marken/
Btw., I checked on a claimed-to-be 900mm/f8 mirror lens in the Size of a 500mm, which you can order under different brand names. That combination of size and magnification would be a sensation, but I learned it's physically impossible. (Just think of this bucket-sized Russian 1000mm/f11!) And apart from the inscription, the 900mm looks like the 500mm offered by the same import firms... I read posts from guys who had a chance to try the "900mm", and they describe it as being Chinese-made, more like 500mm (what a surprise!'), and impossible to focus. Or in other words: Just forget it, it's world's worst 500mm!. If you want a mirror lens for a reasonable price, look for Tokina.
P.s:: Wasn't Alpa sold to China or am I mistaken?