The contemporary version of the rewind icon consists of two arrows next to each other pointing left. The orientation of the arrows is opposite to the direction of the play icon. Historical variations of the icon exist, such as the three vertically stacked arrows of the ReVox reel-to-reel recorder in the 1950's. You can find out more about the ReVox and other early play back icons here: http://www.pushclicktouch.com/blog/?p=57.
Reel-to-reel tape recorders 1960's