Hurd windows from 2001
Hello there. You may indeed have the 39-253LB and 39-253RB; but you also might have the 39-438B and 39-439B. These operators are extremely similar; the only differences lies in the appendage at the end of the straight arm. The 39-253LB and 39-253RB use the 39-529 square-shaped slider, sold separately; whereas the 39-438B and 39-439B use a rectangular slide piece that comes with the operator. The video below explains this in more detail. Check your old operators to confirm which set you need.
In either case, for new covers and handles you can use the 39-375 and 39-376, or the 39-451 and 39-452, depending on the style you prefer. These covers with handles simply snap on the new operator bases. Let me know if you have other questions.