An endoscope can include an elongate, manipulable shaft with a distal-end visualization element and a handle body comprising at least one control surface for manipulating a distal region of the shaft, where the handle body includes a passage through which a length of the shaft is passable, and where the handle body includes a novel connection structure configured for firmly, securely, and removably mounting the handle to a channel of another endoscope in a manner axially aligning the passage with the channel to provide a path of communication for the shaft. A dual medical endoscope system can be constructed including a first and a second medical endoscope, where the first endoscope comprises an accessory channel with a proximal mounting port providing access thereto, and where the second endoscope comprises a handle body that is securely and removably attached to the proximal mounting port.