How to determine sash weight range.

Thanks for posting. Typically for non-tilt window channel balances, any number on the balance should be the stamp code. In any event, if the sash weighs exactly 22 lbs, use the 2540 stamp option for a window sash in the range of 19 through 25 lbs. The weight ranges for channel balance stamp options are meant to describe the overall capacity with two balances installed. Let us know if you have further inquiries. 

It may depend on the identity of the balance. Can you show us pictures of any attachments or fittings at either end of the metal channel? That is how one narrows down balance identity. Ultimately though, if this is a channel balance you will also need to obtain the exact weight of the window sash. That will be the only way to tell us what stamp option the new balance will need.