I picked up this neat old volt meter that I'd like to use on my boat.
The guy I got it from told me it came out of a 1920s automobile. I
figured it wouldn't even work, but when I got it home I was surprised to
see that it did work, and I was also surprised how easily the chrome
cleaned up on it. They sure don't make chrome like they used to.

Of course it's a 6 volt meter. Is there a simple circuit I can build
with parts available at Radio Shack enabling me to use this meter with
12 volts?

I don't want to use a store bought DC to DC Converter because that'll
give me a constant 6 volt output with no fluctuations, even if the input
voltage varies.