crystal window

Can you show me the link arm(s) that come out of the back of the operator and push and pull the window? From there will try and narrow down what you need. 

Thank you. Now, an operator that can close the window has worn down gears and should be replaced. I believe you need either our 39-253RB or 39-439B. These two operators are very similar, save one difference that the video below highlights. Watch to see which you need. In either case, you could use either the 39-376 or 39-452 as a new cover & handle kit, depending on the style you prefer.

I am afraid there's absolutely no way I can tell which one you need from the photo. The difference between the two operators is the appendage at the end of the straight arm, as the video I posted shows. That is not in view in your photo. Apologies for any inconvenience.