Lancaster Beam Approach Indicator AM Ref.10Q/4

Has vertical dial with O /I to left and right and horizontal dial marked L and R (Left and Right) 

There are 2 round mesh grills to either side

Rear marked A.M. Air Ministry Crown marking with Ref.10Q/4 (similar no. to other L/R Gauge) S.47 found by civilian near Harkstede