Black Cat Books
NOTE: Titles originally just said “A Black Cat Book” at top of front cover with no series number. At some point they changed to “An Evergreen Black Cat Book” with a Bx- number.
BA = $.50
BB = $.60
BC = $.75
BD = $.95
BC-60 is the first to use the “An Evergreen Black Cat Book” edition statement and the first to drop the practice of tying the prefixes to price. So BC-60 was $1.45, BC-61 was $.95, etc.
https://www.jahsonic.com/GroveBibliography.html -- lists BC 1-566
Grove Press Starts Mass Market Line, PW, June 19, 1961, at 44.