Rattler,
We added model numbers to our blade stamp in 1972. The next change came in 1986. I have not found a reliable method of determining the age of a Buck knife stamped like yours are. Sometiimes the paperwork will be dated and that helps narrow it down some.
Not particularly collectable, unless they are mint in the box. We made so many of them from 72 to 86.
Hope this helps,