This as of Septimius Severus from my collection is not all it may first appear. It is an ancient cast copy, weighing in at 4.3 grammes, compared to an official as of the period that would likely be in the 9.5 to 11.5 gramme range. It is an example of limesfalschung.
What is interesting to me is that it appears that the same master coin was used to make the mold for this piece as a similar published example from Caerwent (that specimen weighing 4.37 grammes), minor casting blemishes notwithstanding and illustrated above. The cast sprue marks on my piece, below, match the location on the Welsh specimen (also marked in the plate illustration of the Caerwent coin) so may reasonably postulate the same unofficial, probably British, mint produced both.