Buck's marking changed by era rather than following one scheme. Before 1968 the stamp carried the name only. From 1968 to 1972 it was a two-line BUCK over USA mark. From 1973 to 1981 it was three lines including the model number. A formal date-code symbol system was introduced in 1986 and has continued since.
The eras above are the reliable milestones: name-only before 1968, two-line 1968 to 1972, three-line with model number 1973 to 1981, and the symbol date-code system from 1986 onward. Those four markers will place most Buck knives within a band.
For a precise year on a post-1986 knife, the symbol system is the route, and Buck publishes it.
Only what Buck documents itself is reliable. A full year-by-year decoder reproduced from memory or from an unsourced forum post is exactly the kind of fabricated authority we will not publish.
Buck's own How old is my knife page, linked below, is the place to decode a specific symbol.
Buck traces its heat-treating method to 1902 and began commercial knife sales in 1947 as H.H. Buck & Son. It moved from San Diego to Post Falls, Idaho in 2005 and remains family-owned across five generations.