P3D Optical testset ?

[PZuijlekom@xxxxxxxxxxxxxxxx]

I was offered a set of cards (32) the other day (in box) together with
about 100 'home-made' stereo cards (around 1960) and two Holmes viewers.

The set is titled:

Bilder fuer Stereoskopische Uebungen
(Pictures for stereoscopic exercises)

zum Gebrauch fuer Schielende
(for use with squinting people)

By Dr. med. C. Dahlfeld
Published by Ferdinand Enke, Stuttgart, 1921

They are 87 x 171 mm. No 'real' stereo pairs however.

For example there is a card with a table, bottle of wine and two glasses
on the left half of the card and a table, bottle of wine and a chair
on the right half. When fused (in a Holmes viewer) you see a table, bottle
of wine, two glasses and a chair.

A small booklet accompanies this set, describing it's purposes, in German,
which I can read 'fluently'.
The description is not very clear to me however. Was it used for testing
eye-preference ? Thought I saw a comparable set (in English), on eBay,
last week. Does anybody have a clue ? What's this set worth ?

Thanks for your opinion, comments and ideas in advance.
Maybe Alexander Klein can be of any help ? Alex, are you listening ?

Cheers,

Peter