I agree, but I wanted to respect his restraint.Coming from Sato-san, it seems likely. 🙂 I did some searches for a similar icon/logo/symbol (including AI) but didn't come up with anything.
That actually was my first thought, but it looked so much like a lightning bolt I went with the GN hypothesis, though seeing as it was not something that showed up in any production runs that it might have been an experimental unit.Haruo Sato, who runs Nikon's "The Thousand and One Nights" replied in a different forum:
"This is thought to be a mark meaning "tool (工具=kougu)" that was used by Nippon Kogaku."
He said he couldn't be certain, but that is the prevailing thought amongst people who know much more about Nikon than I do.
Knowing my lens is c. 1952, and this example is likely c. 1958, suggests it might’ve been a pretty established practice.Nice catch, I wonder if the seller has any info. Likely not, but maybe worth an ask.