Originally Posted by
Caroline94535
I have a darling Singer 15-91 from 1954. It's the potted motor model...
The numbers after the hyphen determine the model, so the 15-91 will always have the potted motor. Other 15-class variants are:
15-30 early
15-88 treadle
15-89 hand crank
15-90 external motor (with belt)