G.L Murphy Machinery Ltd. was an industrial parts manufacturer established in 1930. They were based in a mill named Imperial Works on the rural outski
Google will give other references, but I liked the photographs here.
It looks as though someone has assembled this camera from spare parts and added the distance scale in feet. In the good old days, many companies has sports and social clubs and this might (I'm guessing) have been useful for things like team photos. It seems perfectly workable, but it's a pity they didn't take more care with the scale. The brolly on the right suggests it was used for actual photography. Can there be a bit of crude retouching?
I hadn't known about Derelict Places, but it looks interesting.