Part identification help needed

Hello there!

Thank you for reaching out to us. We can help with this but I'm afraid we will need more information. Can you show us some photos of the top fitting? That will allow us to narrow down your replacement options. 

The 18-124P is a top sash guide, not the balance's top fitting. In order for me to ID your balance, I will need to see a photo of the top fitting that's attached at the other end of the balance. See the video below for more information. 

Thanks for the additional photos! At first glance, this reminds me of either the S380-31 or S385-31 channel balance. The best match will depend on the depth of the bottom fitting as shown in the image below. However, yours looks like it may be the 15-029 which is 7/8" deep. I recommend you measure the bottom depth of your old bottom fitting to determine the best replacement option. 

Comparison of the S380 and S385 balance shoes.