Same stamp for balance pair?

A handy person from FL says:
I have a 12" balance on each side supporting a window sash with a weight of 6.4 lbs.

On another set of windows I have a 24" balance on on each side supporting a window sash with a weight of 16.9 lbs. These balances do have a stamp, although one side says 2320, the other side 2330. Shouldn't the balances be the same for both sides?

If you could please direct toward me towards the correct balances for the window sash weights for the 12" and 24" balance in the 351 series, I'd really appreciate it.

Thank you
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Paul from SWISCO responded:
You are correct, the pair of balances should have the same weight spring. Going by your sash weights, for your S351-12 the stamp option should be 1120, and for the Series 351-24 the stamp option should be 2330.
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