Not many - my wife's got some old 'buy and hold' certificates in a file somewhere. Its a bit of a pain to trade them - commissions are extortionate!
Incidentally, Scripophily (collecting old share and bond certificates) is an interesting and potentially lucrative way of linking anorak-like collecting tendencies with the markets. I was sent an auction catalogue recently that included a section on old stocks and bonds, there's some lovely stuff out there that would look good framed on the study wall!