Custom balance
Hello,
The channel balance you have here reminds me of the Series 751 Channel Balance, assembled with a knife lock shoe; the clip at the top can be replaced with either the 19-029 short or 19-030 long s-clips (sold separately).
Based on the stamp, I believe your channel should have a 25" length, which means you'll need the S751-25. You'll need to be sure to double check this to ensure that this is the right fit for your repairs.
In regard to the 24X stamp, I am not able to cross-reference this with the stamps from our balances, unfortunately. That said, I'll need to know the exact weight of the window sash to determine the stamp option needed for your balances.
Please don't hesitate to reach out with any other questions you might have.