no stamps on the S380-36 Series Chanels

A quick learner from Odessa, FL says:
August 12, 2020
I have a 4 ft wide, 6 ft High Window installed in a house built in 1988.
I can't find a stamp number on it to determine weight.
It seems to say "Caldwell" and maybe E5 but it is difficult to read.

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Tom from SWISCO responded:
August 17, 2020

Hello! I can see the stamp in your third photo. It reads "35 4," which corresponds to our 3540 option. You can always weigh your sash on a scale to be 100% sure that's right.
36" Series 380 Channel Balance
36" Series 380 Channel Balance
S380-36
$12.27
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