Oldest record; I have over 500 78rpm records, the oldest ones are from the early 1930's, mostly jazz/big band but there are some Harold Bauer and Paderweski discs in there and some old country and western discs from that time. From the 40's I have Moisewistch playing Rachmaninov 2, Kappel's Khachaturian Concerto, lots of jazz and interestingly many 10 inch vinyl LP's, including the original Art Tatum Capitol recording and Charlie Parker's complete Savoy recordings; I expect those might be worth something. The oldest records that I actually purchased and still have are Jimi Hendrix' debut album "Are You Experienced", Josef Krips conducting the complete Beethoven Symphonies and Friedrich Tilegant(sp?)and the Southwest German Chamber Orchestra playing the Brandenburg Concerti.
And then there's Brahms cylinder from 1889 (iirc). It is spooky to listen to these.