I have an engineering office copy of the Colt flash suppressor for the Vietnam era XM177E2 assault rifle.
They were duplicated by the late Robert Roy of Colts on the Colt Engineering office blueprint copier. Perfect full size copy of both the interior and exterior tube with full dimensions.
This is sold as a research item for collectors of Colt NFA weapons and the XM177E2 specifically.
This is $30 shipped in a crush proof tube.