MYSTERY MAJESTIC TRANSFORMER

MYSTERY MAJESTIC TRANSFORMER,  OPT, MAINS  We have this transformer, dunno what it is, is it OPT or mains?  There's some age to it as it was wound at the Bournemouth factory , never used and the details of its winding lost in the mists of time.

One side wound with quite large gauge enamelled wire, other side  with 6 mulitivoloured smaller gauge wires.   I cannot be bothered to map the windings and play about with AC voltages and calculators so my indolent sloth is your gain.