As a sewing machine that is very capable of sewing most anything a home sewist want's to sew, it's an excellent machine. As an investment for resale, it's hit or miss. Singer made a million of them. I currently have 8 of them, three of which are treadles, one is a cabinet machine and the others are portables.
Value is dependent on condition, completeness, and geographical location.
ISMACS {
http://www.ismacs.net/home.html } has lots of information on them as well as serial # charts that help you date the machine.
Joe