Stamps seem to be used on yours, with hand retouching. "Samian" is an old label. The fanciest and earliest
red wares, like
Arretine and some of the 1st c. AD
red sigillata are figured and mould-made, primarily. Those are the ones that get illustrated in handbooks (or else the plainest
red wares, most commonly found in excavations). The patterned ones,
still with certifiable Greco-Roman origins, such as egg-and-dart or friezes of palmettes, are just what I
had trouble finding. The use of stamps in decorating relief ware goes back to at least the 7c BCE.
What is suspicious about yours is simply its nearly pristine condition and the impossibility of checking out the less visible parts of it. Perhaps you could take a photo of the bottom?
Also, I assume it to be beaker-size, say, 12-15cm?
But it certainly is pretty.
Is the clay dense and hard?
Pat L.