AVO Exposure Meter

Ian Grant has sent me the following images and pdf instruction leaflet for an early AVO exposure meter.

He says ".....bought an AVO meter for £2 at a car boot sale over Easter (2010) with it's case, manual etc".
(To download the instruction manual as a pdf, click here).
"I also have the 1939 BJP Almanac advert for it and the similar Smethurst High-Light meter".