Gauge light bulb spec?

I don't know why a 57 would NOT be a good number, they've been around for a very long time:

http://www.gelighting.com/na/busine...ry/catalogs/downloads/auto_08_index_specs.pdf

might be a better one:

http://genet.gelighting.com/LightProducts/images/t04/0000000/r00300v-1.pdf