Olympus as a company was founded in October 1919, the same year as Asahi Optical (Pentax). They started as a producers of microscopes and thermometers under the name Orinpasu Kabushiki-gaisha, but
went into camera production in 1936, mainly producing medium format cameras. In 1949 the company was renamed to Olympus Optical Co, Ltd.
When everyone else started making Pentprism slr cameras, Olympus came up with the Pen, a small 35 mm compact. The
format was 18x24, 35mm cut in half and giving 72 shots on one 36 frames roll. This was in 1959, the year of the Nikon F. A brave move indeed. In 1963 the Pen-F was launched, an porro prism slr camera. It sold a lot, as the quality was very good and the cameras
came with very high quality Zuiko lenses. Besides, they were small and light compared to most other brands.
Still, even if the lenses were good, the half-format couldn't match the 35mm for the pros when they demanded the best. So in 1972 Olympus finally,
as the last of the existing brands, introduced their PP SLR answer. The idea of making small and light cameras was followed up when they presented the M-1. Measuring only 136x83x50 mm and weighing only 510 grams, this was the smallest and lightest PP SLR ever.
Other brands had to come up with an answer, and Pentax made the ME, even smaller and lighter. But that was some four years later, and Olympus had made themselves a name, taking a big bite of the market.
By naming the camera M-1 Olympus had challenged
Leica, who owned the right to M as a model name. Leica warned them of trouble to come, and Olympus soon renamed their M to OM.