Replacing 380 Channel Balances for a 30lb sash

A home owner from Jacksonville, FL says:
Need to order two new channel balances. They are 25" 380, but not sure about stamp. It says 4 9 (small something) then looks like BSI. The window sash weighs 30 lbs. Thank you.
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Donna from SWISCO responded:

We can have a custom balance made, you have two options for a S380-25 balance for a 30 pound sash

2560 stamp will carry a window sash weight range of 28 through and including 30 pounds.

2565 stamp will carry a window sash weight range of 30 through and including 33 pounds.

This information is based on 2 balances per sash. Balances are designed assuming friction in the jamb weather-strip will carry a portion of the sash weight. Suggested sash weights are approximate.

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