Extended travel 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. Our service requires clear and unobstructed photos of the hardware in question at minimum.
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.
Given that this is an extended travel balance, I additionally need to see the clip at the end of the cord. I'll also need you to tell me the exact weight of the sash, down to the ounce, and the quantity you're hoping to buy.