First, 1005 is the Federal Supply Group (FSG) for ordnance materiel. Federal Stock Number 1005-550-8697 (National Stock Number 1005-00-550-8697) is the slide of a M1911A1 pistol. (Bet you knew that!)
So the indication is that it is a replacement slide made under contract to the U.S. or maybe an allied country. I tried to follow up on RAPP/Rapp and came up with a bunch of names; I checked out some, but they don't link to a particular product the company made, only to a CAGE code, so I gave up on that route.