A reminder to remove the PRAM battery from your Mac, or replace it with a new one every few years to prevent this from happening. This was a Macintosh IIvx with its
NewerTech® : Batteries : 3V PRAM Battery for Mac®
MacBook Pro 15" Core 2 Duo Model A1211 PRAM Battery Replacement - iFixit Repair Guide
DIY Power Mac 5200 4.5V PRAM Battery Pack | AppleToTheCore.me