Oldest piece of gear is ME! Oh, wait! I think you meant hardware and such.
Well, there is the Kelty Backpacker (1960, bought from Dick Kelty from his garage, when he was still doing a lot of business from his house in Glendale), Bauer Karakoram sleeping bag (also 1960, but mostly just stays in the gear closet, mail-ordered from Bauer), Aschenbrenner ice ax (bought at Bradley's, a long-closed climbing gear store in Pasadena, in 1959, hung decoratively over the fireplace these days), Terray duvet (down parka, bought from Snell's in Chamonix in 1964, still wear it occasionally), a collection of soft-iron pitons from the late 1950s and chromolly pins (including angles up to bongbongs, Lost Arrows, Leeper Zs), carabiners (including a number of the Alcoa Chouinards). From the early 1960s, a full set of Clog chocks (some of us were using them here at Tahquitz and Yosemite in 1963-64, contrary to some of the climbing history books saying chocks weren't used in the US until the 1970s).
For cookware, I have (and use) my Primus 71L that I got at Bradley's in 1960 (got a lot of stuff in 1960), Barb's Svea 123 she got in 1965 plus the Sigg cooker she got a month or so later.
I still use my old army surplus bearpaw snowshoes (bought at Bradley's in 1959) from time to time - I prefer my 1990's Atlas, though (Perry, the founder of Atlas, created them while a grad student at Stanford as one of his grad student projects in my next-door neighbor's engineering design course).
Except for the snowshoes, I bought all of this stuff new and used it (in some cases, still use it occasionally). I'm not a collector, just someone who rarely throws things out, though I have occasionally sold some items - like the first climbing rope I had. 120 foot Plymouth nylon, bought from the Dolt (Bill Feuer, from the trunk of his car), later traded to Marty Karabin, a super-collector, for a new 60 m Dominator rope from Bluewater.