I cannot appreciate at full scale the size of this device, but it seems to be fully factory manufacturated, not a homemade gadget built using a couple of surplus pieces.
As you have said, the pins looks like a regular US plug, although them could be a pair of Faston male pins also. In any case, this device looks like not having any kind of transformer inside, but instead seems to be fitted with a direct 120 v lamp.
Here in Europe even miniature full 230 v low power lamps (with E10 or B10 caps) are fairly common for signalling uses despite there are not a daily basis.
Regards,
M. Gonz?lez.