What is this transformer doing on the back of my speaker?

i found an old tube radio from the swap shed @ the dump, and it has a speaker with a transformer on the back of it, what is the purpose of this transfomer. i havent tired out the unit yet, im gunna re-wire everything first, its all a mess, but the tubes look to be intact, and the attendant at the landfill said he knoes the person that had it, its fine, just very old and needs new wiring, its an old westinghouse in a custom box, i guess they didnt knoe the value of free operational tube amps.