This looks like a match for our 39-239B awning window operator. Check it out and let me know if ours differs from your original. We also sell the 39-451 cover and handle assembly separately.
A quick learner from Pacific City, Oregon says:
March 25, 2021
Does the part number you mention (39-239B) correct for a Milgard awning window? See attached photos. Thank you.
Tom from SWISCO responded:
March 25, 2021
The 39-239B is used by many different brands. The operator in your photo does appear to be a match to me, though, based purely on physical details.