Ancient PLCs
These chug along for far more than 20 years! I know of several that are still running 24/7 and are getting on for 30, and last year I repaired an ancient TTL forerunner that's something like 40 - the I/O modules are 2x10x8... inches!
Fortunately none of these have any network access (that I know of)
Biting the hand that feeds IT
