Description:

Light exposure meters from the renowned optics and camera manufacturer, Carl Zeiss from Stuttgart, Tysklan. Made in the late 1940s, early 1950s.
1953 was this model replaced for a new one, that had instead of a match needle, used a metering needle on a measuring scale.

The difference in today's light meter is that it used a selenium photocell, which in principle is a solar cell. Therefore, there was no need for batteries but did poorly in dark situations.
This model is refelktiv which means that it measures the reflecting light from the object in mean averidge form.

The messuring dial has settings for film sensitivity (ISO) in both ASA and DIN, wanted shutter speed / aperture to the left as well as the meter could be used for meassuring in filming, displaying aperture in relation to film speed.

The approach of use was to first put the right film sensitivity, then the desired aperture / shutter speed. A meassuring needle showed the amount of light after which a match needle was centered over the meassuring needle and the right combination of shutter / aperture could be read.
The approach made the meter easy to use and very popular.

Zeiss Ikon was formed in 1926 through the merger of four major camera manufacturer, ICA, Contessa-Nettel (retrieved from those in which the ICA and the con that came from Con in Nettel Contessa). The two other companies were Ernemann and Goerz.