Small Unknown Coin

You sure the metal is white (i.e. isn't copper)?

Looks like a very late Roman bust to me (rotate the second photo about 135 degrees counterclockwise). I suspect it's a late Roman bronze from the 4th or (more likely) 5th century, possibly an AE4 - they're generally pretty awful, and tiny.

If you're sure it's not copper, it could be a clipped *siliqua or other silver denomination - the style actually seems to fit better - but I suspect copper (and, IIRC, if the thickness you gave is correct, it's also far too thick for silver).

By the way, are you sure of the size and weight? 1.4 grams seems a bit too heavy, and 8 mm a bit too tiny.

That is a late late roman copper coin, the reverse is SALVS REIPVBLICAE (Safety for the Empire) and shows Victory (a pagan goddess) dragging a bound captive barbarian by his hair (the other line being the wing). not surviving on this example is a trophy, which would have been over the shoulder, formed of arms captured from the rebel barbarians. A mint mark would have been below, probably from the Eastern empire at this point.

The obverse doesn't have enough legend left to suggest who it is, but my money would be on Arcadius or Honorius, based on the style of the bust.

My error, it is copper, not a white metal. Light does funny things.
Size and weight are confirmed, to the limits of my scale and metric ruler.