I have a hard time believing that anyone is faking coins to this level of
quality - with hand
engraved dies - without any apparent profit motive. The emperor and
type are too common and
cheap, and we don't see the market flooded with these as we do for poorer
quality fakes like the "
mule" from the seller you noted.
From a quick scan of the sellers other
LRBs I don't notice other
fakes apart than the "
mule", so I doubt they even realize that one is fake.
Here are a few coins from the
ANS for comparison (plus resized coin under discussion). I don't know what that "pearl" decoration on the cloak is meant to represent, but it's not unique to that coin.
The
officina letter could be a partial theta or B - something similar to one of these
ANS examples.
Ben