Before CDs made the whole subject boring, people went to a lot of effort to get good sound reproduction and long life from their audio recordings, which at the time involved a physical needle being dragged through a groove that wiggled back and forth in the shape of the sound wave to be reproduced. It worked surprisingly well all things considered, but the needles did tend to wear out, so people worried about what they were made out of and what damage they were doing to the grooves when they become worn.
I imagine these chromium ones were fairly low-budget compared to the osmium and iridium needles I have, and of course eventually diamond tips become the standard, before everyone lost interest when CDs came out.
Source: eBay seller donfriend
Contributor: Theodore Gray
Acquired: 25 November, 2003