dearlenbaugh wrote:
I just remembered the Outer Limits first season episode The Hundred Days of the Dragon:
Original Air Date—23 September 1963
"The election draws near and William Lyons Selby seems destined to win. Elsewhere, the communist nation of dictator Li Kwan has achieved a remarkable breakthrough: a serum that renders human flesh plastic. A simple injection and a process of molding allows an agent to quietly murder Selby and take his place!"

Again, no latex, but close.
I believe the Thriller episode(which also starred Sidney Blackmer of The Hundred Days of the Dragon) Premature Burial from 1961/62 had a latex type mask used to con a couple into confessing of murder.