I removed my main power relay to check the condition of its contacts. This relay is able to be easily disassembled, unlike most others. I was surprised to find that the contacts looked virtually new, no wear, arcing, or pitting. Not bad for a relay that probably dates from the 1940s.
I can't find any reference to its part number on the internet but it is a style that is still in production (but modernized somewhat) by Cutler-Hammer & Eaton. This style was predominately used as an aircraft engine start contactor... but what aircraft? Most military planes had 24V electrical systems by then but this relay is 12V. Any guesses?
Regards, Neil Tucson, AZ