A Brief History of the Marque
Company founded by Count Bonmartini to build a motorcycle designed in 1926 by the engineers Carlo Giannini and Pietro Remor. The engine is a transverse verticale four of 490cc of 32hp with a compression ratio of 6: 1 and a 3-speed gearbox.
They built a second model with water-cooling. The OPRA successfully competed in several races, but was too expensive to produce for the existing market conditions.
Sources: MC Storico Conti et al