This is a totally standing-alone AF lens although it was released as a Chinon lens. Its AF sensing and driving systems are located in the front of the K mount and without any AF control across the mount, making it an universal AF lens for all K-mount manual and AF SLR and DSLR bodies, theoretically. However, this AF lens can not be mounted on a body with a projecting eaves above the lens mount (e.g., Pentax K-x DSLR) because the eaves and lens case around the mount block mounting.
It looks funny, strange, or professional?
Once installed, press this green button to go for AF. Its AF speed is acceptable although not as fast as the modern AF systems.
The focusing can also be set manually.
The green LED and a beep tell you 'in-focus'. The green light also falls down to the aperture size marked on the aperture ring that is shown in the v-shape opening above the lens mount. The lighten aperture size can be pick up by a aperture window on camera such as Pentax KX in order to display in the camera's viewfinder. A great design. There is another set of aperture size marks (on the left in the image above) for reading from the lens body directly.
It's manual are in multiple languages. The section in English is posted here.
The case and barrels of Chinon Auto Focus 50 mm 1.7 are made of plastic. I do not open it to look, but will put a question mark behind its durability.