The Mitsubishi company was established as a shipping firm by Yataro Iwasaki (1834–1885) in 1870. In 1873, its name was changed to Mitsubishi Shokai . The name Mitsubishi consists of two parts: "mitsu" meaning "three" and "hishi" (which becomes "bishi" under rendaku) meaning "water caltrop" (also called "water chestnut"), and hence "rhombus", which is reflected in the company's logo. It is also translated as "three diamonds". Mitsubishi's automotive origins date back to 1917, when the Mitsubishi Shipbuilding Co., Ltd. introduced the Mitsubishi Model A, Japan's first series-production automobile. An entirely hand-built seven-seater sedan based on the Fiat Tipo 3, it proved expensive compared to its American and European mass-produced rivals, and was discontinued in 1921 after only 22 had been built. In 1934, Mitsubishi Shipbuilding was merged with the Mitsubishi Aircraft Co., a company established in 1920 to manufacture aircraft engines and other parts. The unified company was known as Mitsubishi Heavy Industries (MHI), and was the largest private company in Japan. MHI concentrated on manufacturing aircraft, ships, railroad cars and machinery, but in 1937 developed the PX33, a prototype sedan for military use. It was the first Japanese-built passenger car with full-time four-wheel drive, a technology the company would return to almost fifty years later in its quest for motorsport and sales success.