Need help determining proper replacement part.

A professional from WA state says:
I need to replace a Channel Balance that is 26" in length and has the markings "24 4 BSI VK" as best as I can make them out. I don't know the proper weight range. Please advise. Thank you.

26-inch/pd/Series-385-Channel-Balances/S385-26
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Tom from SWISCO responded:
There are a few things to consider here. First, be sure to measure only the length of the metal channel; do not include the length of the plastic shoe or plastic top. A 26 inch balance marked with a number 24 is uncommon enough to warrant double-checking the measurement.

As for the stamp option, unless you can find the four-digit stamp (likely starting with a 2) on the old metal channel, you will need to remove and weigh your window sash. Update us about the old balance and we will try to confirm the proper replacement.
A professional from WA state says:
Right, so the metal channel is 24.5 inches long. The only markings I see are as I stated above. The "VK" is aligned perpendicular to the rest of the markings.
A professional from WA state says:
Sorry but the parts I was referring to are the wrong ones. They are replacements but not the same as the original. The original says "25 2 JL Caldwell" and is 26" in length on the metal channel. I think it is a 350 type but am not sure how to determine the weight. Please advise.
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Tom from SWISCO responded:
Thanks for getting back to us! That makes a lot more sense. The Series 350 comes with the 19-002 top and 15-004 bottom, so as long as those match you should be okay. A stamp of "25 2" usually corresponds to our 2520 option, but like Mike mentioned you can always weigh your sash to confirm. We have a chart on the S350-26 store page that tells you how much weight each option can support.
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