Diving into the CBT Tape (http://www.cbttape.org) - a huge collection of MVS open-source software. The current collection is version 498, released 1st December 2019.
The documented revision history goes back to version 20, released on 3rd March 1976. Timestamps on some of the current contents are of similar vintage, and still usable on the latest z/OS. Fantastic.
For anyone interested, it's this one: https://www.amazon.com/SODIAL-CDROM-SATA-Convertor-Adapter/dp/B00LHKRHDK/ref=sr_1_6?keywords=sodial+sata+ide&qid=1576156702&sr=8-6
Though any of the similar-looking ones (two electrolytics near the IDE) are probably identical. HD24 OS v1.21, tested with a 2.5" WD HDD and a Crucial SSD.
What's old is new again.
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