It’s probably a bronze sestertius but I don’t think it’s a ‘VESTA’ coin. It looks to me like what you perceive as ‘VESTA’ is the first part of the titles for Vespasian as Augustus (Emperor) and Consul, reading: 'VESPASIAN AVG COS'. The portrait is consistent with that too.
The reverse looks to be Mars advancing right, holding spear and trophy, similar to this, although not an ‘SC’ (Senatus Consulto) type.
The last part of the legend on that side reiterates his Consulship, as either ‘COS II’ or ‘COS III’ (can’t make it out for sure, except that it’s not ‘COS IV’ or later).
Vespasian was Emperor from AD 69 – AD 79 and was already a Consul at the time he became Augustus. Thereafter he then took the additional title for Consulship each time he was awarded it… as ‘COS II’ in AD 70, ‘COS III’ in AD 71, ‘COS IV’ in AD 73, 'COS V' in AD 74 and so on.