Please help me identify a broken channel balance in an aluminum window of unknown manufacturer

A home owner from Jacksonville, FL says:
The window is one of 13 installed sometime between 1960 and 1998. The lower sash weighs 28-29 lbs. The outside dimensions are W-51" x Ht-25 5/8".

The exposed glass in the sash is: W-48 1/4" x Ht-22 1/4".

The broken channel balance appears to be a Series 380.

The length of the metal channel is 23". The width is 1/2". The length of the spring is 13". The channel bears two stamped numbers: "30" and "2240".

According to your web page and weight ratings, a #2240 is rated for a sash weight of 19-23 lbs. My sash, at 28-29 lbs., appears to warrant a rating of #2260 (27-30 lbs.). I wonder if this weight discrepancy might explain why my window has always been difficult to open and close?

Photos are attached. Thank you for your assistance.
User submitted photo of their window balance.
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Tom from SWISCO responded:
It's odd that the original installers used such a weak spring for such a heavy sash. It certainly explains why your window was hard to operate before. If you can confirm that your sash is 28 to 29 pounds, then I would definitely recommend the 2260 (it's always good to double check anyway, just in case).

Either way, you may want to consider our Series 385 as well. This is similar to our Series 380 except the shoes are different. You do not show the depth so I can't be sure, but just eyeballing it, I think the Series 385 may be closer. Please confirm.
A home owner from Jacksonville, FL says:
I have measured the bottom shoe depth according to your earlier posts and photos. It appears to be a 1" (15-005)shoe, not 1 3/32. I assume this means it is a Series 380 channel balance. See additional photos.

I weighed the sash again. It is 28-29 lbs. Does the "30" stamped on the metal channel indicate a 30 lb. weight?

Concerning the Option 2240, which I have now, vs. the suggested Option 2260 (weight range 27-30 lbs.) Just to be clear, is it correct that my sash weight of 28-29 lbs. should require TWO channel balances, each rated 2260?

Is it necessary that I also replace the top sash guides, which I have not removed and do not appear to be damaged? Thank You.
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Tom from SWISCO responded:
Great, thanks for clarifying. If the shoe is 1" deep, then our Series 380 sounds like the best match. I don't see a 30 stamped on your balance, but it could possibly denote the sash weight. I wouldn't depend on it, though. Every balance manufacturer uses a different coding system and there isn't really any uniformity to it. That's why it's always best to get the weight of the sash, so that you know exactly what you need.

Our sash weights are determined assuming that two balances will be supporting the weight in question. Therefore, if your window weighs 28 to 29 pounds, then you will need two balances with a 2260 option.

If your top sash guides are in good condition, there's no reason to replace them.
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