I lost the original post about the '57 truck with a 12-volt electrical system with a burned out 6-volt flasher.

If I recall correctly, the post noted that the vehicle had a 12-volt alternator installed. I did some looking about, and as late as 1963 at least some Jeeps had 12-volt systems with conventional generator/three-terminal voltage regulator systems.

If the vehicle in question had an alternator, it probably had been modified at some time, replacing the generator with an alternator. The 6-volt flasher probably was just an Oops ...

"What you see is what you have ..."