Colt A2 Carry Handle/Rear Sight/Scope Mount

Metal genuine Colt AR-15 Adjustable Carrying Handle Assembly (carry handle / rear sight / scope mount) purchased used from a pawn shop outside of a US military base. The day of purchase I attached it to and removed it from my 6940 to be sure it worked, set it in the cabinet, and have never used it since. I'm not sure what the blue writing on the bottom is, perhaps a control number or inventory number, but it feels like it would clean off without too much effort.