The Lloyd Bloch version of Moonstone first appeared in Captain America #169 (1974) and was created by Steve Englehart, Mike Friedrich and Sal Buscema.
The Karla Sofen version of Moonstone first appeared as a gun moll of the villain Dr. Faustus in Captain America (vol. 1) #192. She later appeared in issue #228 of The Incredible Hulk where it was revealed that she was the psychiatrist of the former Moonstone, Lloyd Bloch, and that she tricked him into relinquishing the moonstone to her. She was later revealed to be a member of the shadowy organization known as the Corporation.