Benjamin Light Meter Model B (Weston E703). c1940, USA Manufacture. Weston made a number of bespoke models for major electrical suppliers and installers. Benjamin were a major installation company internationally. As the back plate indicates, this meter would have appeared in their trade catalogue. The light readings are divided into zones to indicate suggested minimum lighting levels for various workplaces and occupations.
The use of the term 'economic results' to describe the zones is interesting. It suggests that energy costs can be reduced by keeping below the maximum level of the relevant zone. It also suggests that working productivity (and uneconomic accident avoidance) can be optimised by setting lighting levels within the specified zone for an activity or environment.