I haven't had any luck figuring out the size of this bulb for my switch panel I am building. This switch panel has 120v bulbs that have 44tw stamped on it and I need to figure out what the 12volt size would be. Thanks for the help.

It looks like what you have is a miniature single contact bayonet base. This may be of some help.

Light Bulb Base

Differences are not just on the socket but also on glove shape, filament shape and wattage. The socket identification is just one of them, but glove shape, filament and wattage will make lot of diff too, even to be able to melt a lense using the wrong bulb.

for an interested guide the parts manual shows this... valid for anything ( taken from a Mopar 74 catalog... but the same for most )

Good info there, never realized it was in a Mopar parts manual. Learned something new again!

You're pretty sure the bulb you have is 120V? I have only seen that style bulb in low voltage form. All of my old pinball machines use the 44/47 bulbs and a lot of guys replace the 44's with the lower draw and cooler 47's but those are all low voltage. Of course this is just my own experience.