It could also be needle length. My old W&W had a different needle length and it was very difficult finding the correct needles for her. An old dime store had a big round tin with a dial and you turned the dial to get the correct bin to pluck out your needles which were in wooden tubes. Yes, I am ancient too. You are saying ...Whaaat? I think those are gone with the Zenith upright radios, but this was in the 50's.