Do you sell this Caradco casement arm?
We unfortunately don't sell an exact match for this operator. This is a very old design that, in my opinion, isn't precisely compatible with any of the parts in our inventory.
That said I think you can get something like our 39-014 to work, but it's going to take some retrofitting on your end to fit. To start with you'll have to drill new installation holes in the sill. The wheel at the end of the arm is also much smaller so you'll need a new track to match; that would be our 39-505. This will also require drilling, and note that it's designed to install on the face of the sash, not it's underside.
Lastly, I'm concerned about the shape and general style of the base. It may not be a big deal but you should be prepared to make alterations to the sill trim that covers it. In a worst case scenario, you'll need a carpenter to make up a new one.