Go here and browse for the model 221. Just a quick statistic.
Feb 9, 1947 20,00---Nov22, 1946 20,000---Oct 25, 1946 10,000 (221-1)----Sept 16, 1946 20,000
There were lots of FW made in the 'day' that we all want. Here is the site
http://www.singerco.com/support/serial_2letter.html
Wow Sharon, you had the same idea as I did!!!