Window sash 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.

Thanks! This looks like it might have to be a custom made balance. I see that the shoe depth is well under 1". Can you verify its exact size for me? 

We do sell the 7/8" deep 15-029, but this isn't a stock option so a custom assembly is required. If that is the case, I will additionally need to know how many balances you wanted to buy altogether. You may also want to get a sash weight to be safe; your old 28D stamp usually corresponds to our 2840 option, which holds 23 through 28 pounds, but it can't hurt to check to be safe. Custom balances can't be returned for a refund.