The first has been reblued, so the takedown lever is probably the result of a repair.
The second has also been reblued in the past. Interesting combo, but can be assembled by anyone anywhere at any time
The third is a parts gun. Note that the receiver is not notched. My best guess is that this started out as a normal commercial AE and that someone fitted an arty barrel. Note it has no notch for the rear sight.