I would suggest perhaps one of you contact your HQ. I know at Theta HQ, we have a staff archivist (in addition to our volunteer archivist and volunteer historian), and I bet you all have something similar in Kappa. I bet they could research this and/or get in touch with your Keepers.
best of luck - I hope this amazing key ends up in a very special-to-Kappa place.
Jane
ETA
this link which may or may not be the same Annie Bell Sargent. Since the eBay posting does not list a date, I'm not sure.