I don't think the Style-Mate is generally considered a collectible Singer, but the $25 price is good if it is in working condition. Could make a nice backup machine. I would be sure it sews well before purchasing it, as for this model you probably don't want to pay for replacing the electrical cords, missing parts, etc.
Edit: Found this web discussion:
http://www.sewgirls.com/sewing/singe...uty-20734-.htm
And here's a different view of the same machine, which is why I mention it can make a good backup machine:
http://www.flickr.com/photos/girl_lo...ee/4305221741/