I have an indicator on my phase converter. Salvaged from somewhere.
It is a 120 volt bulb, 3/4 inch diameter, and a double contact bayonet
base. The base is 15mm diameter.

I tried for hours to find any conversion from dimensions to bulb
number. No luck.
Can anyone shed some light on where the specs are located for the
various
bulb types?

The catalogs and web pages list hundreds of types of bulbs, and what
base they have, but not the dimensions of the base standards!
How many sizes of bayonet bases are there?
Where can I get one replacement bulb?

Thanks in advance.
Pete