Cheers man, yeah it was incredibly lucky. So glad to have it - its like new inside - the original lamp was burned out with the arc tube ruptured and that building hadn't been used to my knowledge in the last 20 years at least and closed off to the public so I reckon it burned one lamp (it was an old 80's tube in it), then simply sat dormant since until the power was cut.Thats an awesome save that, really well done and great timing too. Regarding a manufacturer, I'd like to suggest GE, the cover looks very similar to that of my Tris 2D bulkhead.
Could be GEC; it'd be interesting to see if there are similarities to yours, but the choke in it is an Italian choke so I'm starting to wonder if its an Italian fitting? The mystery continues!