RIA Quality Hardware Rebuild

Picked up what turned out to be an odd Quality Hardware on Gunbroker recently. It's odd in that it went through a rebuild at Rock Island Arsenal, but the rifle retains it original flip sight, type one barrel band and even what appears to be its original highwood stock (intact) with type one barrel band marks on the nose only. The stock is stamped RIA over FK on the left side , but there are no proof P's anywhere else on it. From what I can see, the only parts changed out are for sure a type 3 sear marked RIA and possibly an extractor marked IN I found in the bolt. This seems to be more proof that rebuilds could run the gamut from totally rebuilt to very little like this carbine.

Since the stamp for the inspector is FK and not the seemingly more common EB, then it would have to have been "rebuilt" there sometime before July 1946 when Frank Krack was there. Another great question would be where did it go after that for the last 70 years? I suspect some of that time has been in someone's closet.