Window balance

A quick learner from San Jose says:
My window balance is labeled 27 4 Caldwell. It is 28 in long and 1/2 in wide. From looking at your site I think it is a s350 but I don't understand the 27 4 as a tension option
Thumbnail of the uploaded file named Stamp code
Thumbnail of the uploaded file named Balance shoe
Thumbnail of the uploaded file named Balance top
A quick learner from San Jose says:
I'm thinking S350-28 with 2740 option but please check my options
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Casey from SWISCO responded:

Hello,

I agree that your balance resembles the S350-28 (2740). The determining factor would be how the specifications from our product page compare to yours. The 2740 strength option will support a sash between 19-26 lbs. as shown in the chart under the balance product description. Thank you! 

Close up view of the S350 balance top.
Close up view of the S350 balance top.

Close up view of the S350 balance shoe.
Close up view of the S350 balance shoe.

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