Based on the New Italy Hoard (Hersh NC 1977), Mattingly holds that the denomination the Dodrans (3/4s of an as = 9 unciae) was first introduced by C. Cassius, not M. Metellus (2004: 220). This rules out his original theory echoed by Crawford in RRC that the type was introduced by the later to provide a space to commemorate a divine ancestor via the legendary Caeculus. Why would Cassius create a new denomination for Vulcan? Mattingly gives a terse answer: “The Vulcanal near the forum was the center of popular and tribunican activity in the early republic.” No footnote. It’s a hard assertion for which to find much support.
Does it have anything to do with Liber on his other new denomination the bes (2/3s of an as = 8 unciae)? What do Vulcan and Liber have in common? Not much but we do have his intriguing passage:
That the two gods could be linked is shown in this little passage from Hyginus’ Astronomica:
This text however seems to me another explanation of a common artistic motif “Hephaestus’ return to Olympus”:
The narrative might go back to a lacuna in the Homeric hymn of Dionysus, some speculate. The narrative is mostly deduced from various vase paintings with the help of this passage in Pausanias: