Playing record stamper on turntable

I volunteer at a local museum digitizing oral histories and other audio content from cassette and reel tapes, and I have been using Audacity with great success. Recently the archivist presented me with with some record stampers that were from recordings from a local musical group from the 1960s. He asked me, “What are these, and what can you do with them?” I first thought that since these were negative impressions of the records that the undulations would be impressed on ridges rather than grooves, so they wouldn’t play on a conventional turntable. But I thought I’d give it a try anyways. The first problem was that the rotation would have to be reversed so I played it with the normal clockwise rotation starting from the lead out groove at the center of the stamper. Surprisingly it played rather well, although in reverse. I recorded it in Audacity and then used the reverse effect so I could play it back in the correct direction. I was amazed how well it sounded. It seems that the stylus was essentially tracking against one surface of the ridge. The ridge actually seemed to be pushing the stylus and the next ridge was not contacting the stylus. I recorded in stereo and occasionally there was some distortion in the right channel which I suspect was the face of the adjacent ridge. No doubt, I am not extracting the full stereo content, but it was an interesting experience and an example how I used Audacity.

Most interesting - thanks for sharing this.