A particular stereoviewer...

Here is a special stereoviewer i would like to show you

This is a folding stereoviewer made of chromed metal parts and wood

here is how it looks like when unfolded.

viewing lenses can be adjusted using a pinion rack

Stereoviews are attached together making a roll allowing a no end viewing by turning the wood buttons on the top sides

I havn't any informations about manufacturer, there are no marking anywhere. According to views displayed in this sample (Pilgrimage of Lourdes), i guess it could be French...(?)