Webcor "Magic Mind" Question

[AUdubon5425]

I've been wondering just which changer I have in my '57 Webcor Prelude - the tags are long gone from the changer.

Does anyone know the difference between a Webcor 1641 and a 152?

I'm hoping someone just might have some old service guides laying around. Cosmetically these look identical to me - there had to be some change made to warrant a new model number.