It's a 66. If you like it, it's worth what you'll pay for it.

Additionally, it has the "red eye" decal set that many people like. As for value, that's specific to your area and whether you want to keep it or resell it. It's almost impossible for any of us to determine that for you.

There are only a few that if you said $50 that we would all tell you to jump on - 221, 222, 401, 403, 500, 503, 411g, 421g, 401g, 431g, 12 - that's probably most of the list of Singer machines that regularly go for more than $50.

The other thing to note is that almost invariably we pay way more than we should for our first couple of vintage machines. It's not a bad thing, just a learning experience.

Is there a motor on it? Does it come with anything else? I wouldn't pay $50 for just a treadle head, unless it was in fantastic condition.

This is a good reference for identifying machines:
http://www.sandman-collectibles.com/...r-machines.htm

Also Rain has some tips on his http://vssmb.blogspot.com site

eta: here: http://vssmb.blogspot.ca/search/label/identifying