Optician's Eye Testing Set.

This set was acquired by me during a clean out of E. Esdaile & Sons, situated 42 Hunter St.Sydney, back in 1957. Various unclaimed items were offerred to the staff who worked there , (myself included). Esdailes were a scientific & industrial instrument makers. They also did repairs and testing of surveying, optical, medical instruments etc. I was told that the item above was a travelling opticians eye testing kit, for rural areas where people were unable to get to a city optician.
The set is almost complete 1 or 2 lenses missing. Each lens is individually engraved with its magnification power. Also marked on the slot for each lens on the box itself. All of the lenses are unscratched & clear. Would be interested if anyone could add to the use of this item if any.