Tiberius/Augustus dynastic mule

An odd coin, certainly official, given the style, high quality silver, and weight (3.7g). This piece combines a reverse of Augustus, featuring Caius & Lucius, paired with a Tribute penny portrait of Tiberius. This is interesting since more than 12 years elapsed between the last issue of C&L denarii and the first issue of Tiberian denarii. Ironic, since the succession issue was long settled, and yet here was Tiberius, inadvertently legitimizing the long-dead Caius & Lucius as successors!