Help identifying replacement 27 4 F O Caldwel balance

A home owner from Arlington Heights, IL says:
I need to replace four window channel balances. The Balance measure 29" from the bottom to the top of the top balance shoe. The channel of the balance measures 9/16" square. I have attached pictures of the shoes and I need your help to recommend which model balance to buy. The balance has the following stamped on it: "27 4 F O Caldwell".
User submitted photo of their 27 4 F O Caldwel balance.
Profile picture of Donna
Donna from SWISCO responded:
Looks like our 28" Series 380 balance. For the stamp "27 4" choose our stamp option 2740.

Let me know if you have any additional questions.
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