Charlie poses for sculptress Katherine Stubergh during the filming of Modern Times, 1935

Stubergh & "Charlie." From  alvarezwax.com

To make the figure, Stubergh first made a wax impression (casting mold) of Charlie's face and then he sat for her while she sculpted the fine facial details. Two casts were made, one of which was sold in an auction just last year for $25,000.