The Salvus Ferrara, Salvus Ravenna and Salvus Bologna are all burglary-resistant safes, certified according to EN 1143-1 Grade 1. The difference lies in the fire protection.
The Ferrara is not fire resistant. The Ravenna offers 30 minutes of certified fire protection for paper (LFS 30P), the Bologna a full hour (LFS 60P). That extended protection requires a heavier build: the Bologna has a multi-walled structure filled with a special fire-resistant composite. The Ferrara and Ravenna have thinner walls and therefore offer more interior volume at comparable external dimensions.