Hey there,
Your balances appear to be the discontinued crossbow style balance. These have been converted to use our Series 795 Channel Balances. Specifically, yours appear to be the S795-21.
To confirm that these balances will be a situatable replacement, you'll need to obtain a few measurements from your existing balances. These include the diameter of the balance channel/tube, which should be 1/2", although there is a chance it could measure 3/8". You'll need to obtain the width of the bottom T-shaped attachment, as well. It will either be 1" or 1-1/4" across the bottom of the T shape.
You will also need to obtain the exact weight of the window to select the correct stamp option.
Take a look at the video below for instructions on this balance conversion and the information you'll need to determine the correct balances. Let me know if you have any questions.