The body shows markings 45411 and the arm shows 31876. The teeth on the arm gear have broken off.
Tom from SWISCO responded:
August 7, 2020
Hello! Please see our 39-221B operator, 39-451 cover and handle, and finally the 39-545 stud bracket. I think these parts match up to what you have now, but look them over and let me know what you think.