Window spring 26c bs1

Your window balance appears to be the S795-26 with a 26C stamp option. This balance comes assembled with the 15-195 1-1/4" closed cam shoe, but you'll need to double check the width of the shoe and whether the cam is closed off on the back. 

If the cam is open, you'll need the 15-195B, which is sold separately. Another possible shoe is the 15-194 1" shoe, these are only available with a closed cam.