The two Case knives should have pattern stamps on one of their blades. The first of those two looks like a 'baby copperhead' pattern (maybe 62109), with jigged brown Delrin handles and mfr'd sometime between 1965 - 1979. Look below the 'USA' stamp on the clip blade's tang to see if any 'dots' are there. If no dots at all, the knife was made in the 1965-'69 time frame (per the 'USA' stamping, which wasn't used before 1965). If there are dots (how many do you see?), it'll be in the 1970 - '79 time frame. Depending on the number of dots, that'll decode specifically which year. 10 dots in 1970, then subtracting a dot for each year after, until only one dot is left for 1979.
The other Case shows a 1989 stamp on the tang, revealed by the 'lightning S' in the 'CASE' stamping's angular font used during the '80s; the single 'dot' indicates the last year of the decade (1989). Also looks like a copperhead pattern. Look on the other sides of the blade tangs for the pattern#. Handles look like jigged 'amber' bone.
Not sure about the 1st knife shown. Maybe an inexpensive import; looks like the stamp only shows 'STAIN' 'LESS', if I'm correct?
The Buck knife shows a model# 825 stamp. Probably mid-80s mfr (based on the '1986' in the commemorative artwork). Stainless steel, either 425M (earlier) or 420HC, which is what they've been using since, to present day.
I can't quite make it out, in the picture; but the last one (small stockman) should also have a pattern# stamp on the tang, ending in 'UH' most likely, for the 'Uncle Henry' line produced by Schrade. Synthetic 'Staglon' handles, very similar to Delrin. The '+' after the 'SCHRADE' mark indicates stainless steel; that's probably 440A, as used by Schrade for most of those. Likely 1970s - 1990s, maybe post-2000.