OK some REALLY interesting info now...
I suspect the BMS is manufactured by KANTHAL -
http://www.kanthal.com/
Follow the products section to 'Thermostatic Bimetal' and the data sheet for the TB1577 is there.
However, no information about the differing suffix 'A-GE' compared with '-GE'
So I'll email them now and we'll see if they reply. If not, I'll email from Work :-)
We'll get there soon....
I can feel it in my bones....