cabinfever

A FW is a model 221, and a Singer. There really weren't any others (to my knowledge) that had the flip-up hinged bed, except the 301; the big sister to the FW 221. The FW is smaller & was "THE" portable sewing machine of it's day, & still loved & used today. They were mostly black, with a more rare white or very pale green.
Here is the link as to where the model # appears on the machine itself: http://www.singerco.com/support/model_number.html
This link shows (near the bottom) that the FW was made from 1934 to 1946: http://www.ismacs.net/singer_sewing_...al_number.html I thought it was made a little later than that, but perhaps this page at Singer is focused on a certain date range.

I got mine from a sewing friend who still owns at least 8 other FW's, & about 60 total machines, which she maintains herself.
For those who want to maintain their own machine, a great help is to get the DVD "Those fantastic Featherweights" with David McCallum. Even though it is intended as everything you need to know to clean, maintain & restore a Singer 221 FW machine, you will really understand any of your old Singers. He also covers how to restore the old cases which may have developed a musty smell or replacing broken handles & latches; this DVD is 3 hours looooong & very thorough. He does talk about the 301 as well. You will find the locations for oil & grease (gears) shown in detail, and are common amongst most early Singers. Happy sewing on the oldies but goodies.