I have searched the usual sources, but can find nothing about aplanat sets.
This has 4 separate lenses which can be screwed together when not in use and placed in a tight brass can. Focal lengths are 16, 25, 28 and 54 cm.
Lens is engraved size 3 bis and the fixed aperture (wheel stops) is only 1.5cm. Serial number (if this is meaningful!) is 33606.
My guess is that this is a portable aplanat (F around 16) with perhaps suggested use of single lenses as a landscape meniscus?
It came on an 18x24 French "Chambre Touriste" and certainly looks like the original fitment.
Both guesses and facts would be useful?