Here is my 1957 Asahi Pentax. This is arguably the world's first commercially successful SLR. I say arguably because there were a few SLRs produced all the way back to 1933 with Exakta in Germany, and the better known Contax S from 1948.
The success of the Asahiflex line provided R&D capital for Asahi to develop a Pentaprism based camera and in 1957, a model named "Pentax" was released. The camera was extremely well received, so much so that Asahi decided to change the company name to the one we are familiar with today; Pentax.
Other manufacturers followed with similar designs, notably the Nikon F which was released 2 years later in 1959.
1957AsahiAsahi PentaxAPPentax Cameracollectable camerasPentax OriginalOriginal Pentax1957 Asahi Pentax
From Asahi Pentax - AP, S and K models