For those unfamiliar with those early coin-op stereoscopes - a brief survey:
The German-made Kalloskop seems to be one of the earliest and most successful machines. It is dated circa 1895 and credited to Polyphon Musikwerke of Leipzig by Nic Costa (Automatic Pleasures). It contained between 18 and 24 stereo tissue cards often presented in 2 series of 9 or 3 series of 8, thereby squeezing a few more coins from the punters. The chain of cards were advanced by pressing the knob at the front and a glass panel on top of the case provided illumination. There was also provision to hook an oil lamp on the rear for further illumination.
Early coin-operated stereoscope from around 1900 pictured on page 54 of Wenn der Groschen fällt...
The impressive cast iron multi-station stereoscope, Princzess Panorama was produced in 1895/6 by the pioneering maker of chocolate vending machines, Deutschen Automatengesellschaft Stollwerck & Co. (DAG).
The Autocosmoscope is credited to L.V. Automatic Company Ltd. and dated 1898 by Nic Costa. However, other sources attribute it to Haydon & Urry Ltd. Gameswat was restoring the below example in 2009 (see Autocosmoscope - great name). He has it as 'Haydon & Urry, 1896'. Which is correct?
Haydon & Urry produced a film projector called the Eragraph in 1897 and (according to Costa) the Erascope around 1905.
Another early British machine is the metal-clad Automatic Stereoscope (see below and in the Museum). Perhaps Sweetmeats has more information about this one. Currently it contains some wonderful stereoscopic dinosaur images.