Rod,
The years prior to 73 are pretty easy to distinguish in most Bear models. I have most of the Grizzly years 1953-70 where I stopped collecting them.
Joe,
From 73 on the Grayling Grizzlies are pretty much the same as far as I know. It would be interesting to find out if there is a way to put a year on them by serial number or some other means.
I bought another one from that time period yesterday.