My guess is that the transformer is probably from the the original, or subsequent installation where multiple speaker systems were fed from a 70 or 120 volt distribution line.

While i don't have a clue about that particular brand or model, those transformers usually tend to fall short of what we'd call "hifi". Altec's Peerless transformer division made some of the best in the business, and i think it's still a preferred practice to avoid their use in hifi applications if at all possible.

If you don't have a use for them or value them in any other way, they can be a source of quality magnet wire for various DIY hifi projects from wiring tasks to winding your own inductors.