Be careful tho...my Singer 9W doesn't "follow the rules". I was so excited to think that according to the serial number on the machine, that it was made in 1879. It wasn't.
The good folks at Needlebar.org got me straightened out on what I have. I have a beautiful 9W, made by Singer after they aquired the Wheeler & Wilson plant. The serial number on the machine is a W&W number and not a Singer number...my machine was made in 1912, which still excites me, especially after I saw Billy and one or two others mention that it's a sought after machine... :) (Not counting the fact that I just simply love the thing, no matter when or where she was made!)