[quote=Greeter EvaWhere do you find the model 221 on the machine? I can find the serial number , but not that one. What does that number really stand for?[/quote]
A lot of the machines have a small plate under the Singer seal that says 221, often with a "J". "K" or "1". 221 is the model number (just as the first Singer I ever bought was a 237). If you aren't sure what your model number is, go to this site and find your serial number.
http://www.singerco.com/support/serial_numbers.html