Adjuster screws - yes.
Shimano - very likely from how they look.
It is funny, I was in my hobby workshop this morning and took some photographs. Not one of them show the rear dropouts... I will check the next time I go there.
The point of me going there was to check the fork steerer tube for information. Many times there are stamps and/or something else that can give information. I was lucky this time again.
A message from Italy somewhere around 1990. And now we know what they called this colour. Verde Germoglio. Translates to "green sprout" - a young plant. Maybe there is a better translation - any Italians here?
I also want to clarify something I wrote in the original posts here. When I wrote "smooth welds" - I meant they have been made smooth after welding. How - I do not know without ruining the paint. It could be brazed on material but there are other alternatives also.