It appears to be 27" 385 channel balance

Thanks for reaching out to us! There is a chance our S385-27 Channel Balance could work to replace your existing hardware, but I'll need to confirm a few details to determine if this is the right fit. To begin, may I please see a photo of the pulley system in the center of the balance, where the string and spring meet? You may need to find an undamaged balance to obtain this photo.

You'll also need to be sure to confirm the measurement for the depth of your bottom shoe. It should be either 1" or 1-3/32"; there is also a chance it could be 7/8", if so please let me know. Take a look at the diagram below for reference.

Profile view of a winged balance attachment