Looks like it's a Singer 66. Cabinet looks in great shape. Look over the treadle to make sure it is ok, no cracks. If some of the black (japan) on the bed is gone then ask for less. You didn't state the price.
Here is the Singer serial # id site for info:
http://www.singerco.com/support/machine-serial-numbers
Serial number is found in right front corner on the plate with numbers.
If there isn't a manual, here is a link:
http://www.a1sewingmachine.com/manuals.htm
I clean all my machines with Singer sewing machine oil only, inside and out.
There are lots of youtube tutorials on how to treadle machines and using the bobbin winder. Have fun with her!