Window operator sawtooth part malfunctioning

A home owner from Connecticut, USA says:
It seems the original one is from Acorn, can you please help me to find a correct replacement? Thank you.
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Tom from SWISCO responded:

We don't sell this exact operator, but we do sell two alternative parts that may still work for you: see either our 39-142, which has an 11" long arm, or the 33-407, which has a 13-1/2" long arm. You just need to pick whichever arm matches your existing size.

The only catch with both options is that these are face-mount operators, meaning the screw mounts these from the inside. This is in contrast with your rear-mount operator, whose screws mount from the outside. The good news is that we sell the 33-205 thread nut. This acts as a kind of adapter that will allow you to mount both the 33-142 and 33-407 from the outside, same as your old part.

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