Replacement Window balance

I'm not sure what you have, unfortunately. That stamp not a product code or anything, it just indicates the strength of the spring. However it is notable in being an extra heavy-duty spring, so keep in mind that your balance will very likely need to be custom made.

Before we can go into that in more detail, however, we still need 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.