I was at the Richmond VA gun show today looking at an AR-15 marked Match HBAR with a serial number that started with CMH.  The barrel was extremely heavy and stainless steel, much thicker than the 6724 but it was not marked.  The upper was also not marked Colt.  The dealer did not know the twist rate of the barrel and claimed that this was all Colt.  Any clues as to what this might be.  i know that I am missing something here so feel free to ask questions.

Thanks