Originally Posted by sewbizgirl

I had fun poking around a flea market today, searching for old machines... I have really been wanting to get a 15-91 for FMQ. I found a Singer with the serial # Y8821760, a treadle. When I looked it up online it said it was a 15K. Another one I found was a 15-90... So, how much difference is there between a 15-90 and a 15-91, and also a 15K?