You do know that the (spring loaded)firing pin on a 1911 is shorter than the space that it occupies within the breach-block, eh?....In other words, when the hammer is "down", the firing pin does not touch the primer. It must be cocked or else the hammer can't "throw" the pin into the primer and therby cause the pistol to discharge....so no-cocky, no-shooty....And futher more, if ya take a close look at the original 1911 hammer, you'll see that it is both larger and different in shape than the more modern renditions. That is because, as designed by the late-great John Moses Browning, it was designed to be carried hammer down and that particular hammer shape was the most natural for both cocking AND "uncocking" WITH ONE HAND by mounted troops, whom by the way, had to use their other hand to control their horse. Yeah, there was still a lot of fighting done off horse back at the turn of the 19th-20th century....As to it's "half cock" position, that is not (and never was intended to be) a carrying position. Just as with Colt's half cock notch which had been provided on their SA Army Revolver of 1873, the notch is there on a 1911 solely to arrest the hammer fall should the operator's thumb slip off of the hammer while cocking the gun....Of course, none of the above applies to guns with worn or altered springs, or guns with out of spec replacement parts, or guns which have been subject to alterations by well-meaning but basically clueless "tinkerers"........Point to all this is yeah, it is quite safe to carry an as-issued 1911 with the hammer down on a loaded chamber. I myself, did it that way during the years I spent as a Texas lawman...and still carry a 1911-A1 that way today....Hope this helps to clear the matter up.
DGW
I am not expert on show but I believe he carried 1911 for the later dates of show. His mentor was killed and his mentor carried 1911. Not sure if Gibbs carried that particular example 
