2015-1978-1967.

The image on the left is from Nov 2006 at an OCB contest he guest posed at (the Yorton Cup in Pittsburgh, PA). The two images on the right are from Chet guest posing at the Oct 2007 Yorton Cup in Washington, DC. Chet was born June 1, 1939 so he was 67 and 68 in these pictures.
Chet spoke out against steroids his whole life. Those who may not believe he was drug free may not understand the difference genetics can make. Chet was genetically gifted. Try to find one photo of Chet with "moon face". You won't.
Chet is lifetime natural. Arnold was only 19 when he lost to Chet, and if you look at the photos from 1966 you'll see Arnold was "fat", meaning not very conditioned. A lot of people would have beat Arnold the way he looked at 19 at that contest.