I've got a timberline from the same year. Seatpost is stuck, so I'm trying to remove it in a manner in which I can re use it.
I did put a vernier on it last summer but can't remember what it was. I googled the measurement though and it didn't come up with any seatposts that size... Next time I top up the penetrating oil, I'll measure again. It'll be tomorrow if I remember.
Did you try T-cut to restore the paint?