A phono cartridge, believe it or not. A Grace F9E purchased in 1979. In 1983 I upgraded it with the Ruby stylus, and had it installed on a SOTA Sapphire with Magnepan Unitrac arm, which I still use. The cartridge is presently at Soundsmith awaiting re-tipping.
Work priorities constrained the amount of listening I could do during a lot of the intervening years, helping it to last so long.
Regards,
-- Al