Small French Viewers
In the early 1900's the French created a new design of stereoviews in 45 X 107 mm and the slightly larger 60 X 130 mm or 6 X 13 as it would become know. In 1907 Auguste and Louis Lumiere invented the first color photographs and they were called Autochromes. A huge variety of stereoscopes were developed for this new size and they were quite popular. Also for the first time an amateur could photograph his own stereoviews.
The largest producer in France was the Richard Company. The Company was founded in 1845 by Felix Richard. In 1882 two of Felix's sons formed "Richard Frères" or the Richard Company. The Richard Company produced several different forms of stereo equipment as well as a variety of scientific instruments such as barometers, thermometers and chronographs. Jules Richard managed the Company into the 1930's.
A. Mattey of Paris was perhaps the most innovative maker of stereo apparatus in the world. He produced various photographic items starting in the 1890's and some of it was still in catalogs in 1948. Mattey purchased other competitors and had several addresses in Paris over the years. Products were sold under the "Star" brand and "Unis France" brand and they were sold by retailers throughout Europe.
The following photo's show a few viewers by Richards and Mattey.

A variety of small viewers. Note the center viewer is also a Richards camera.

A Birds Eye Maple Case with 96 views of France in 6 X 13 format.

Three Omnium viewers and a walnut box of color Autochromes.

Stereospect from Germany has a magazine for 12 views. Pressing a lever moves the next view in place and a new magazine is loaded for other views.