You can find random PDP, VAX, even X86 systems that have lifespans 20+ years. As for a single boot probably a much smaller corpus, maybe some forgotten Sun SPARC in a telco on -48V DC power bus.
A VAXCluster or Sysplex(S/390) would I guess be more analogous but those can be a bit Ship of Theseus since you can change the hardware out over time.
A VAXCluster or Sysplex(S/390) would I guess be more analogous but those can be a bit Ship of Theseus since you can change the hardware out over time.