p.s. - the bronze decorated iron shield boss is marked Legio VIII AVG 
that's "Legion 8 - Augusta" Legionary Animal was the Bull.
formed in 65 BC by pompey the great, julius caesar took it over in 49 bc, ocatavian reconstituted it when he was emperor, hence the cognomen 'augusta', it served for 400 years thereafter. 
LINKY 
The Bull was also a mithraic symbol. i can't quite make out the latin scratched into the left border, likely the owner & his assigned cohort, it appears to be marked  'the property of junius dubilitatus'.