De Zeng Retinoscope 1915
De Zeng Retinoscope was called Ideal Electric Retinoscope 280.
It is marked De Zeng and patented Aug 25 ’03. (see image)
It has a battery-holding handle. It it turned on by rotating the rheostat on top the handle.
There is no slide mechanism to change the focus. There are the letters DEZ and ENG on either side of the mirror. These are meant as fixation targets for the patient being examined.
These are described as illuminated letters because there are slits in the tube next to the bulb so that light can spill out and shine on these white-on-black letters.