1. The opening (for gear bore) is about 3/8 inch. (Photos are, Imag0992 and Imag0993
2. The photos (Imag0990) showed the dimensions.
3. I cannot find the logo of Anderson on the casement window.
Dave Sr. from SWISCO responded:
March 8, 2018
I believe your operator is similar to the Truth 39-022. This type of operator takes the 39-114L handle, which clips on without using a set screw. Looks like that's how yours works, too. I would just make sure the hole diameter is 11/32".