Lawson series SH-7500 Aluminum single hung window

Hello, Maurice. I think we can supply this balance, but it looks like yours has a heavy duty spring so it may need to be custom made. Before we go any further, though, I'd like you to clear up a few minor details. 

First, how many did you need, exactly? Please also look at the diagram below and tell me which choice better matches your current balance.

In the meantime, I'll look into the availability of this heavy spring and let you know once I have an update.

Comparison of the S380 and S385 balance shoes.

Thanks for confirming. That means your window doesn't have to be custom made after all, though the 3650 option would be too weak in this case; that only carries 30 through 35 pounds and your stamp indicates a sash weight of 45 pounds. I would recommend the 3970 3670, but only if your sash is exactly 45 pounds. If it's even a little heavier, get back to me and we can see what we find.