unknown sash weight for Series 152

A contractor from South Jersey says:
August 9, 2017
Is there a formula to estimate the sash weight? I am no longer on the job and don't typically have a scale to weigh the sash anyway.

A large sash 37.5 x 25 has coils marked 3 but won't stay up. Could these be the wrong coils?

Or are they just worn out? Everything looks intact and not broken. There is just one per side.

Thanks for your help!
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Paul from SWISCO responded:
August 15, 2017
It's tough to say. Going off of just the sash size tends to be unreliable, as there are just too many little variables that could affect the overall weight. Based on the sash size alone, I would estimate it to be about 16 pounds. If this is accurate, I'd recommend our S152-8 spring. At the end of the day, the only way to know for sure is to weigh the sash.
4 lb Series 152 Coil Balance
4 lb Series 152 Coil Balance
S152-4
$4.70
8 lb Series 152 Coil Balance
8 lb Series 152 Coil Balance
S152-8
$4.90
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