Maker's Name: 
Hamblin, London
Where made: 
26 × 3 × 2.8 cm

The operator views through a peephole in the upper thumbwheel. Rotation of the thumbwheel selects lenses of different powers.

Illumination from a battery-powered filament, is reflected into the eye through a 45 degree mirror, which has a peephole for the operator.

The line of sight is the same as the line of illumination.

The lower thumbwheel varies the aperture of the peephole, to vary the depth of field.

These thumbwheel adjustments allow the operator to determine the eye's power, and to view different parts of the eye, from front to back.