Block and Tackle for Window

A quick learner says:
Hello,

I need help identifying a part. It is a block and tackle and the window does tilt in.
The bottom panel that tilts weights 19.5 lbs.
The block and tackle is about 29" long
9/16 tall and 9/16 wide

Hope you can help...Photos attached....Ron
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A quick learner says:
It does have some marks on it:

2900 BSI kk
Profile picture of Paul
Paul from SWISCO responded:

Thank you for posting. See if our S770-29 channel balance will work as an alternative to your part. If so, then you will go with the 29C option, that holds a sash weight of 18-23 pounds. 

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