Set of 12 trial lenses and pair of trial frames in purple leather covered case, made in England(?), 1880-1920

Each of the 12 glass lenses can be inserted into the blue metal frames. This changes the way the light is bent when it enters the eye. These lenses may have been intended to assess what a person required in their spectacles. However, the thickness and unusual shape of the lenses indicate they were used to test patients with severe sight problems. The case is punched with the initials of the original owner, “Dr M.”. The set was sold at auction and bought by Henry Wellcome in 1928.