Originally Posted by
Macybaby
From ISMACS - 115 is the class, then there is 115-1 which is treadle, and 115-2 which is handcrank.
For the Domestic machines, Singer normally used the suffix for minor differences and updates to the basic model. With Industrial, it can be totally different machine if it's got a different suffix.
that explains a lot to me. thanks so much for posting this.