I have a theory that it might have been medical equipment because it *appears* to have much better than usual isolation barrier between what is assumed to be the primary and the secondary.hi Scott.
Do you know which type of equipment the transformer was originally powering.??
BTW: did a web search for that Toshiba code, inconclusive.
If I am right about the way this transformer is wound, the primary is inner most and fully enclosed within a section of the bobbin and the wires to the terminations are also fully enclosed within the same section right up to the pins which are then shrouded by an extension of the enclosure around the primary winding.
A normal transformer with a low voltage secondary needs an isolation barrier in the order of 6.4mm creepage and clearance between primary and secondary. For medical equipment where a patient may end up physically connected to the equipment, directly or indirectly, the barrier is more like 10mm creepage and clearance. In a small-ish transformer this can be a problem so the fall back position is a barrier formed by solid insulation which only needs be 1mm or so thick but must be guaranteed to have no voids or otherwise be less than the required thickness anywhere and everywhere it provides the isolation barrier. I have seen bobbins that do this by being in two halves with one sliding into the other and the core then going around both as if they were one single item (ie in the normal way). Vacuum impregnate with a suitable varnish / polyurethane and hey presto, medical grade isolation barrier fully formed.
I am thinking that the yellow band is either an electrostatic shield or just insulating padding to stop the windings buzzing. It can't be a flux band because it is inside the winding window and the heavy metal surround would probably answer for that anyway. If the outer metal housing could be tested for hardness it might be found to be mhu metal in which case it is definitely a magnetic shield and therefore the equipment was probably sensitive to stray magnetic fields, as one might expect medical equipment to be.
Just a thought with a long rambling explanation. Could all be bollocks or maybe right. Who knows.