Well, according to wiki and other sources :
"Though Colt has focused its attention on carbines with 14.5-inch barrels and rifles with 20-inch barrels, Colt continues to make carbines with 11.5-inch barrels, which it calls Commandos. Commandos are assembled from whatever spare parts are available, so Model 733 Commandos can have A1-style upper receivers, A1-style upper receivers with case deflectors, or A2-style upper receivers, and M16A1-profile 1:7 or M16A2-profile 1:7 barrels."
From what I understand, these carbines were completed from available parts. So it's not unusual to see A