Unfortunately, you are simply finding further proof that these are
cast fakes...................unless these coins were traditionally
cast 1500 years ago (which I do not know)................and you just happened to find 3 coins with identical flans and dies after a couple days of searching....................and you knew at least 2 were authentic.......and..................
You see, it's the flans that are the concern...............you can only get this from casting, and casting is how the vast amount of
forgeries are created. If you are collecting a series that was traditionally
cast, then you have a challenge in discerning authentic from
fake................and then you have the mess you have here.
You will need to assume these are
fake cast copies, unless you can prove otherwise. You know the cliche.............looks like a duck.........quacks like a duck.........................then it's probably not a unicorn.
BR
Mark