Series Y consists of my design Groups H to M inclusive, and represent the old Classes I and III. They are a continuum, although it is more difficult to detect this than in Series X.
The die engraver sometimes lacked inspiration and allowed certain types to remain almost unchanged, save for arbitrary differences placed in the designs for the sake of change alone. he was, perhaps more versed in iconography than the engraver of Series X, or at any rate he would allow himself to explore "variations on a theme" that would only be visible if someone knew the 'secret signal' and gathered together just the right coins - a fascinating exercise that I have never seen repeated anywhere else!
The mint site was an undiscovered location west of the River Rance. Very few of these coins strayed east compared with those from the east side of the river that came west. This probably shows the direction of the Roman advances in the area.
The coins were struck at a hot temperature. The dies were thus cut deeper than those of Series X that were struck at a lower temperature. While this made the impression from the reverse (hammer) die often very crisp, the force was absorbed by the plastic state of the metal and the obverse (anvil) die's impression is often rather weak. Another feature of the hot striking that is encountered is the edge porosity. This again is caused by the rapid expanding and cooling of the metal as it is being struck.