Eye eye....
This fantastic set of eye charts is still in the original portfolio folder with hanging chain
It is the "Super Union Astigmatic Chart" Registered No. 3290.
It features six different charts in total, three of which have moveable parts
When flipped over, the boards are held in place with a metal catch
The folder measures 57cm x 39cm when folded, and 57cm x 76cm when hung
A really rare example