Casement operator

The window operator you have here appears to be an older version of either the 39-028E Ellipse Style Single Arm Operator or the 39-413 Offset Single Arm Operator. The difference between the two is the offset in the arm; otherwise the rest of the dimensions are the same.

I've also tagged the other compatible hardware and accessories below for your review.

Dimensions for 39-028e

Alternate view of 39-413