Watch looks very nice and all original, except for possibly the end-links as you mentioned.
I was around in 1974 and they definitely had felt tip markers then. Highly unlikely that markings would last on a non-absorbent surface like metal for 45 years. Besides, at that time, watchmakers usually used small engravers to make service marks.
It might have been more recently serviced, but you should at least have it inspected by a watchmaker to be sure.
Hope this helps,
gatorcpa
Click to expand...