Iron Man, Vol. 3 #84 (2004)

Avengers Disassembled - Turf War, Part 1: When Worlds Collide
The U.S. Government informs Tony Stark of the Arsenel unit that predates the ones the Avengers fought earlier, and task him to find it without informing the other Avengers. He doesn't tell a soul, but given the nature of Arsenel, it doesn't take long for the others to figure it out.
Release Date: 2004