Thank you for viewing. Functionality is unconfirmed. While there appears to be no damage upon visual inspection, please examine the images carefully. Please purchase if you understand that this is a used item. AI-generated response below: This is a mount adapter for Tamron's "Adaptall" or "Adaptall 2" interchangeable lens system. The Adaptall system is designed to allow a single lens to be used with various camera bodies from different manufacturers, and by changing the adapter, you can change the corresponding camera mount. The adapter in the image is marked "PENTAX K.M.", indicating that it is for use with Pentax K-mount cameras. "Adaptall" and "Adaptall 2" have the same physical lens mounting portion, but Adaptall 2 adds the function of transmitting the lens's maximum aperture value to the camera.