Andersen 31 operator

We have a customer with very old Andersen windows that need two new operators (1 left, 1 right). The arm measures approx. 5/8" wide x 7-1/2" from tip to where it starts to angle going into crank cover. This measures approx. 3-3/4" wide x 1-1/2" deep. As you can see from the photo, the arm has Andersen 31 stamped on it, and also has an unusual mounting bracket on the end. Any thoughts? Thanks.