She grew up as "Popo," but took her pen name as her personal one, going by Abby to everyone who knew her. Esther grew up as Eppie, and never used her pen name to friends and family. Just hearing that the twins' names were Eppie and Popo makes me smile.
Rest in peace, girls.
I'm not sure of the year on this one, but I'm better late 50s. And how about that early IBM Selectric typewriter? That was some pretty fancy typing, for those days.