Pivot lock shoe?

Your balance shoe reminds me of the 15-177 Coil Balance Shoe but you'll need to remove the existing hardware and compare the dimensions to be sure.

Alternate image for 15-177

It is compatible with the Series 152 Coil Balance, which is attached using the 33-072 screw. The support, used to hold the coil springs in place, is made using the 15-143 Coil Bushing, 15-144 Coil Bushing Cap, and 15-145 Coil Support Barrel. All three are used together to make the support.

Please see the video tutorial below for instructions on selecting the correct coil weight option.