Wow, I was way off... I thought I remembered being told that GM went to 12v in the early 40s or so. Thanks for the info.
Some older military stuff is 12v that I've seen, seems they were just a bit ahead of the consumer market. Kinda like nowadays we see Uncle Sam with more 48v stuff and more modern cars with 24v.
Buick and Olds went 12V in 1953. GM generators and starters that are 12V are marked and usually red on the tag. Black tag and no voltage means it's 6V. Your genny is worth a few bucks if the tag on it comes back '38 Olds, but for the most part the generators aren't worth a lot anymore - one yard I used to go to the guy had probably 1000 or more.. and they took them apart, melted the copper out, and sold them for s**** as a pile of copper and a pile of short steel.
We sold 8 tons of copper and steel cases a few months ago. The chinese are going crazy for raw materials.