I recorded no output voltage from any combination of the red and yellow wires when supplying 120VAC via the lightbulb safety

I'd measure winding resistance on the black wires and each pair of secondary wires. Then I'd connect 120VAC to the black wires without the light bulb; the size of the transformer leads me to believe that it's intended for line voltage.

EDIT: corrected typo on voltage

 

Thanks!
I shall do that and report back here.
Stu

 

I shall do that and report back here.

Measure the resistance between the black wires; that should be the highest resistance if they're the primaries. If the white wire is a tap for use at 120VAC, you'll measure half the resistance between white and black.

The secondaries should have lower resistances. From the color coding, you have two secondaries.

 

I would agree with dual secondaries. Black and white are typical power colors in the US.

if you can sacrifice one, the primary would be the winding close tot he core.

Resistances is the first thing you have to do. Low resistances are tough to measure accurately, but the info will yield some information.