The Singer site says it was manufactured in 1915, but you'll have to call them to find out exact dates.
Here's a place you can ID the machine by it's features:
http://www.sandman-collectibles.com/...r-machines.htm
Good luck!!
And $50 is not a bad price for any Singer in fairly good condition. As long as it's not locked up with rust it can be cleaned up and parts replaced to make it very useable.