Only tryout issue. Created by Len Wein and Marv Wolfman. Marv Wolfman in Alter-Ego #113 (October 2012) says that originally Johnny Double was to disguise himself as a potential victim of assignation or murder. That concept later became the Human Target.
The central drawing of Johnny Double was drawn by Jack Sparling. It first appeared as a promo piece(signed by Sparling)in On The Drawing Board Vol 3, No 4 (aka The Comic Reader # 68), July 1968. Info per Nick Caputo.