My oldest kit must be my restored billhooks and axes. All proper vintage, some 1950s, some 1920s and the odd Victorian piece. Then there's my old rucksacks- a larger one and a smaller one, both external framed Karrimor from the 1970's or so. These things I have bought more recently, as vintage.
But things I have had for years, that's more difficult. I have a Leatherman Juice from (I think) the early to mid 1990's, one of the early ones. (Recently relegated to "special duties only" it as it has sentimental value and I don't want to lose it). Buried somewhere I have a basic SAK from the early/mid 1980's.
Quite a bit of my basic kit is from the early to mid 1990's as that's when I had garnered enough £££ to get my own stuff rather than borrowing my dad's old kit including his Trangia (late 1970's), Phoenix sleeping bag and tent (both early/mid 1980's).
GC