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.
Information above is far from complete and not terribly accurate. See CNA 1923-1935
Sources: MC Storico Conti et al