That is a singer model 12.
if it is the original irons then it is most likely pre-1885 (when the cross support on the treadle irons was changed)
There should be numbers stamped into the plate on the bed on the right side where the stitch length regulator is.
There are two numbers. the larger one is the dating number. if you get it, I will look it up for you.
NOTE: It looks like this one MAY have MOP (Mother of Pearl) in the bed. the design on the top looks like the ones used with MOP
$100 is a good price for a Model 12 in the original cabinet. Coffin/Bonnet lids are not too hard to find. If it is a MOP machine then $300-$500 would be closer to a fair price
The black wheel indicates that it may have been made for the overseas market. (Chromed item were subject to a "luxury" tax and so by painting them instead they were cheaper to import.
Last edited by SteveH; 12-30-2013 at 04:51 PM.