window channel balance with stamp 1240/ X on the metal

A home owner from Phoenix, AZ USA says:
Looking for replacement window channel balance. The existing ones appear to be original to the house built in 1983.

The metal channel measures 13" by 1/2" width, 5/8" depth. Looking for a replacement that includes the plastic guides (shoes?) at the top and bottom. Which series would be appropriate replacement?

Let me know if you need additional information. Thank you!
User submitted photos of a window balance.
Profile picture of Tom
Tom from SWISCO responded:
Hey, thanks for posting. I've narrowed this down to two possible channel balance Series: either our Series 351 or our Series 390.

Now, as you can see, the only difference between these two Series is their bottom shoe. The Series 351 uses the 15-002 while the Series 390 uses the 15-001. I can't quite tell what you have based on your pictures, though. Please carefully compare their dimensions to your own hardware and see which is a better match.
Comparison of <a href='Channel-Balance-Shoe/pd/Replacement-Sash-Support-Channel-Balance-Shoes/15-001'>15-001</a> & 15-002
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