I personally love the older singers. After spending so much time on the 476 I was amazed at the simple precise inner workings on my 15-91. Also look for the 99, 66, 15-90 and if you can find it the 221.
There is more info here http://vssmb.blogspot.com/search/label/identifying about identifying and in general at the main sight here http://vssmb.blogspot.com/
This site has a many in depth walk thru's for many of the simple fixes for the singer machines. It even covers some of the more popular newer machines, like the 237, 401a and such. Like I said before I just personally like the looks of the older singer machines, especially the shinny black ones with the gold lettering and curvacious necks. I convinced my wife it wasn't just a sewing machine it was also an antique. I now just need to get ride of the ugly cabinet its in and finish the wiring.