Searching for Casement Operator

This looks like either the 39-253LB & 39-253RB, or the 39-438B & 39-439B. The only difference between these two sets is the appendages at the end of the link arms. The former set uses a square shaped slider, the 39-529, sold separately. The latter set uses a rectangular slider that comes built-in with the operator itself. This difference affects window compatibility, to be sure to compare with your old hardware to confirm which you need.