How do I identify a vintage Singer sewing machine?

So, how old is my Singer sewing machine? To identify when a model was made, you need to first find the Singer sewing machine serial number. The number can be found near the on/off switch on newer machines, and on the front panel or on a small plate on older machines.

How do I know if my singer is 15 91?

If its a 15-91 or 15-90, it will have minimal decals on the arm, just saying SINGER with some slight flourishes (see top photo).

How much is a singer 15 90 worth?

The asking prices on these machines runs from $100 - $400 and they seem to be selling faster than some other models (of course, the Singer Feather Weight is the all time favorite).