Finding a replacement balance

I'm not sure what you have, unfortunately. We have dozens of different balances with that stamp. It's not a product code or anything, it just indicates the strength of the spring.

In order to figure out what Series this is, I need you to remove an undamaged version of this balance from the window and show me clear pictures of the top and bottom nylon fittings. I will also need to know the dimensions of these fittings.

These are perfect, thank you! My recommendation is the S385-26 with a 2550 stamp option. I feel confident this is what you want, especially since your shoe appears to exceed 1" in depth.