Moon Landing C Rock

I thought I'd heard most of the "Neil Armstrong and Buzz Aldrin were standing on a sound stage" theories, but this one was new to me.

In one photo from the their famous landing, you can see a rock that clearly has the letter C on it (shown below).  Conspiracy theories say this rock was a prop and the C was its code letter (just as if there was a Rock B and Rock D, etc).  Unfortunately, this one was left turned towards the camera.  NASA says it was a piece of hair or imperfection with the camera lens.

Just some references for the "C Rock"...

http://www.braeunig.us/space/hoax.htm
http://www.studyphysics.ca/apollo2.pdf
http://www.conspiracy-theories-hoax.com/apollo-moon-landing-hoax-camera-problems.html