Not quite obscurity given the attackers could measure the disk and do a quick Yahoo search. Maybe, security by antiquity?
Both. There was an episode in the second `gig` of GITS anime that showcased this model to secure a character's secret ledger before hackers fried his brain.
For a brief period, I kept a copy of my /etc/passwd and keyfiles on a HiMD disk with an RH1.
I’m curious now because I don’t recall the episode - what was the episode title?