Replacement channel balance

I am looking to purchase a couple of 15 inch replacement channel balances. The balance is just a shade less than 3/8 inch wide, so I assume 3/8 inch is the correct width. The length of the balance is 15 inches, from one end of the metal unit to the other (this length does not include the plastic pieces).

The window was manufacture by Radco, and was installed 21 years ago.

Note that the top plastic piece in the attached picture has one of wings broken off.

There are no visible markings on the balance. I believe it was originally marked in ink, but there is now just a totally illegible smudge.

The window weighs 5 lbs. I tried replacing the balances with ones marked 1420, but the spring on the replacement was way too strong. The original balance has a spring length of 6 1/4 inches with a total of 57 coils. The replacement marked 1420 also had a 6 1/4 inch spring, but with 79 coils--this was too strong for the 5 lb. window.

I'm guessing that your 15" SERIES 800 CHANNEL BALANCE Product Code S800-15 with the 14A option is the correct one, but not 100% sure.

If the replacements work, I will likely be ordering several more for other windows.

Thanks for you help.

A couple of more pictures

Sorry, made a mistake.

The overall width of the channel balance is actually a shade less than 5/8 inch, not 3/8 inch as mentioned above. Definitely a bit wider than 9/16 inch, though. Probably 19/32 would be the closest measurement in English units

So Product Code S800-15 is not correct. Not sure if the width would be considered 1/2, since it's a bit wider than 9/16.