It looks like a model 15-90 to me which is considered to be one of Singer's heavy duty hard working machines. They were often called Farmer's wives machines because I guess they were used to mend a lot of overalls and farm work clothes. Singer made and sold a lot of these machines and they have a good straight stitch and use any low shank attachment including the Singer buttonholer or zig zag attachment. That is a good price for this machine and I think you would like the bigger harp.