I went to the South Forks Historic Railway yesterday, and got there a couple hours early(unintentionally)-while waiting, I wandered around in a junktique shop and found a box of automotive bulbs(I'd call them indicator lamps)from what I'd guess to be the '30's, judging from the box.(specifically, #51,single contact miniature bayonet base)
The box is in marginal shape, and everything has a layer of crud on it- I haven't tested them yet, and I don't know if they're all good or not. Manufactured by a company called Royal, but some of the bulbs say GE Mazda on the base. Cost? Two bucks for a dozen. Scott