replacement for aluminum window operator circa 1954

A home owner from Michigan says:
I am trying to replace an operator that looks essentially identical to your item # 39-002 except that the straight portion of the arm is only 8" instead of 9". The total length of the arm including the angled portion is 8 1/2". The unit that the arm is attached to is 5 1/8" long and the inside distance between the double screw holes is 3 7/8". The total length of the operator from the tip of the arm to the end of the portion that it attaches to is 11 3/4". Do you have an operator that fits these dimensions?
A home owner from Michigan says:
A clarification on my original question: the distance from the end of the arm to the center of the gear is 9". I'm not sure which is the measurement you use in your product descriptions.
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Tom from SWISCO responded:
Thank you for the clarification! We use the distance between the center of the wheel bearing to the center of the gear. I will repost this image here for your convenience:
Dimensions for 39-002
Dimensions for 39-002
If you were to use this measurement, do you get 9"?
A home owner says:
That dimension on our operator is 9", the same as what your picture shows.

One other question - If the arm is steel, how do you prevent corrosion, both from moisture and from a bimetallic reaction with the aluminum frame?
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Paul from SWISCO responded:
The material this operator is made from is die cast aluminum. You can spray oil on the operator and rub it down every so often or give it an additional paint.
Anatomy of a casement window
Anatomy of a casement window
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