Truth replacement part
Thanks for posting. Without seeing the entire operator assembly, including the link arm(s) that push and pull the window sash, I can't be certain as to what you have. That said I suspect you likely have either the 39-031 & 39-032, or the 39-155 & 39-156. The difference between these two sets of operators is the length of the link arm. See the illustrations below for reference. Compare both with your old hardware to see what matches best. If neither type of assembly seems right, I will need full pictures of your old operator, arms and all, to find something better.
That's a huge help, thank you! It looks like you only have one arm here, which is the split arm. I agree with your assessment 100%: it looks to be an older version of our 39-035, which means you want the opposite handed 39-036. I agree with you that this is our closest option and I feel confident it will work.
That's great to hear! Just let us know if there is anything else that we can assist you with.