RIC 872 (Vesp), BMC 192 (Vesp), RSC 60
Rome Mint, 76 AD
Obv - T CAESAR IMP VESPASIANVS; laureate head of Titus, r.
Rev - COS V across field; Eagle stg. front on garlanded altar, thunderbolt in claws, wings open, head l.
I'm not quite certain what the meaning is behind the reverse (Vespasian also issued the type). The BMCRE hints that it might be a reference to the death of Mucianus which occurred around 76 AD. Mucianus was the governor of Syria who helped Vespasian rise to the purple. The interpretation here would be the eagle as a symbol of the after-life.
I've always had my doubts about Mattingly's reading of this reverse type.
the eagle when depicted on a funeral pyre or altar would represent an apotheosis type. Here there is no such pyre or altar. The eagle sits upon a garlanded base, clutching a thunderbolt (on my example not well rendered), with no legend referring to the eagle specifically. The following are the three main symbolic meanings of the eagle in the Roman world: as an attribute of Jupiter, a symbol of the Roman legions, a funerary type. In the case of the above coin, my guess would be the eagle is in the guise of Jupiter since a thunderbolt is clutched.