No markings!

Your coil balance shoe can be replaced with the 15-180 Coil Balance Shoe. To determine if it is the correct replacement, you'll need to carefully review and compare the dimensions below. 

Alternate image for 15-180

It uses the Series 190 Coil Balance Spring, which is attached to the shoe with the 33-073 screw. To determine the correct coil weight options, you'll need to look for stamps/markings on the springs. If they are missing or hard to read, please see the video tutorial below for instructions on how to select them.

The 15-181 Double Support Detent Clip, used along with the 15-182 Balance Bushing, anchor the springs to the window track.