Cannot identify spring

A quick learner from Nashville, TN says:
Cannot find a weight on spring or carrier, just "C" and "L" stamped on end of spring. Double coil springs, single hung, double pane, vinyl window.
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Tom from SWISCO responded:

Your old shoe looks like our 15-177, which is compatible with our Series 152 coil spring. Look these parts over and let me know what you think.

A quick learner from Nashville, TN says:
Shoe looks like a match! How can I tell what weight spring to use? There isn't a number stamped on spring. Just "C" on one, "C" and "L" on the other. And can I obtain complete assemblies? Both sides have some wear and tear on them..
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Tom from SWISCO responded:

The "C" might indicate 3 pounds of support (since C is the third letter of the alphabet, which is the logic some manufacturers use). That would be our S152-3. Since you have two balances per side, that adds up to 12 pounds of total support. You can weigh your sash on a scale to confirm that it does in fact weigh 12 pounds.

I'm afraid we don't sell these particular parts in complete assemblies. If you needed new covers, you could use our 15-143 bushing, 15-144 cap, and 15-145 drum. These kind of sandwich over the spring and work the same was as your originals.

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