How does 39-243L attach?

The 39-243L handle has a 3/8" spline type hole, not a hex hole. It does come with a set screw to secure it to the operator. It was popularly used on Ualco operators, who have since gone out of business.

If the 39-243L is not what you have, you can send us a picture of yours so that we can find a good match. We will also need to know the size and style of the hole.