Just because your are enough of a camera buff to be interested in such esoteric devices as 16mm subminiature cameras doesn't mean you always want to be beleaguered by the need to set exposure manually. Mamiya attempted to solve that need with their Mamiya-16 Automatic subminiature camera, introduced in 1959.
Based upon the earlier Mamiya Super 16, the 16 Automatic replaced the slide-out viewfinder with a selenium cell light meter. This is the camera's biggest advantage. By first setting the film speed, then dialing in the preferred shutter, one could turn another dial to line up a needle with the meter readout, thereby "automatically" setting the camera's aperture. Sure, you are still doing it manually, but at least it seems somewhat more automatic. Given what that term has taken on with today's cameras, it may not seem like much, but in the late 1950s, this was quite the feature.
Mild sarcasm aside, the Mamiya-16 Automatic is a solid, subminiature camera. While a bit on the boxy side, it does boast an all metal construction and an excellent Mamiya-Sekor 25mm f/2.8 lens - three elements in three groups and an aperture range of f2.8-16. It even included a built-in yellow filter and flash shoe. The image size is a compact 10x14mm exposed onto 16mm film, itself loaded into proprietary cartridges. Nowadays, locating the cartridges necessary for loading film is always the hardest part of getting one of these cameras up and running. This persistent search will be rewarded as the Mamiya-16 Automatic is a very fun camera to have in your pocket at all times.