I need a window opening part

A quick learner from Toronto, Canada says:
As the pictures show, my several window openers are not working well, they are Truth parts,for they were used for many years and their last three teeth are worn out,and can not closed and open the windows completely. I need to buy the parts to replace them.
In order to chose a right one, I want to try first and buy one, if it is a correct one, I will buy more next time.

User submitted photos of a window operator.
Profile picture of Tom
Tom from SWISCO responded:
Hey, Phillip. See our 39-253L and 39-253R first and let me know how well these match your operators.
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