AMT and Ertl/Esci/Scalecraft and Italeri should have their own book someday
A lot of older AMT/Esci/etc aircraft kits can be found in Italeri boxes today,,,,,,,,,but, not every kit, by a long stretch (all notes are 1/72 scale related)
AMT had an A-4E/F, the kit was the same as the Ertl/Esci/Scalecraft kits, but, is in no way related to the Italeri/Testors/Tamiya tooling,,,,,,,and AMT had an A-4M, it was a Matchbox molding, again, no relation to the Italer/Testors A-4M kits (and that makes AMT's A-4E and A-4M completely unrelated to each other)
same deal with the AMT F-4S, it was sold as AMT/Ertl, and is not the same tooling as the Italeri F-4S,,,,,,,,,,also, the Esci RF-4C is not the same tooling as the Testors/Italeri RF-4C
on the other side of the coin,,,,,,you can get the old AMT A-7 Corsair II (and Esci/Ertl) by getting the new Italeri A-7, the old AMT/Esci/Ertl F-8 Crusader is sold by Italeri as the F-8E,,,,,,,if it is old Esci toolings that you really like, some of them were done by Revell Germany, also
for most of these in 1/72, I can take side by side pics, in cases where the internet says "they are the same" when they aren't, or says "they are different" when they are the same
best way to find out about where a kit came from is exactly what you did do,,,,,,,,ask on a forum
Rex