Coil springs broke, need left & right. Please advise if S140-10 is correct?

A home owner from San Mateo, CA says:
Window is 10 lbs, coil is half-inch wide, etched [#6.5 35"] with no other identifying markings. I do not know window mfg. Is the S140-10 correct for this fix?
Thanks, Jeff

PS: I do have photos, but "add photos" button doesn't.
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A home owner from San Mateo, CA says:
Further comprehension of your product info suggests I need a L/R pair of S140-5, right?
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Tom from SWISCO responded:

I don't believe the Series 140 is what you want. Based on what I see here, your pivot shoe looks like a match for our 15-199. This is compatible with two different kinds of springs: the 1/2" thick Series 160 and the 3/8" thick Series 165. You'll have to measure the thickness of your old spring to confirm which one to go with.

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