The AVO exposure meter was made by the catchily named Automatic Coil Winder And Electrical Equipment Company Limited. Not content with shortening it to memorable ACWAEEC the company wisely used AVO (Amps, Volts and Ohms) as their trade mark. They were by far the most prominent manufacturer of general electrical measuring instruments in the UK for many year and their multi-meters were recognised as the best by professionals - until digital meters replaced moving-coil meters. The meters you see here were their venture into the lucrative exposure meter field dominated by their rivals Weston who were also into electrical measurement meters.
The two meters shown are varients of model - the sligtly newer meter (on the right) has an easier to use dial. As you can see, the meter is quite deep and has a large selenium cell deeply recessed into the front. It's aiming accuracy is enhanced by two internal baffles.
The meter has only one sensitivity range but is surprisingly sensitive. The black pointer is aligned with the red needle by turning the dial, and the exposure read off. Speeds are in the H&D scale (Hurter and Driffield) from 200 to 5000.
The meter originally came in a leather case. One was bought at a boot sale for £6 and the other on ebay for £6.50.
We don't have a date for this meter but the art deco style of the lettering suggests 1930s.
This is a Metrovick meter, made by the Manchester based Metropolitan Vickers Company from 1938 until at least 1947. The main dial is set so that with 23 Schneider rated film and f8, the shutter speeds can be directly read off. The calculator, which was part of the leather case, allowed other aperture/film speed combinations to be used. Although very old, this meter is still working and accurate enough to be used.