Window channel balance code 2820

A quick learner from Ormond Beach FL says:
Hi- The steel windows were installed in 1982, when the house was built.
The window channel balance is 29 inches long. The code on the side of the spring balance is 2820. We have no idea of the manufacturer of the windows. The depth of the window channel balance is 5/8 inch. I need a price on new wndow channel balance units. Thanks. Peter Gilfoil
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Bob from SWISCO responded:

This appears to be either an S351-29 or S390-29 . The difference between these two balances is the depth of the bottom nylon shoe, or the 'heel-to-toe' measurement, so compare both with your old hardware to see what matches best. For a stamp option choose 2820. 

S390vS351
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