File:Signal Mirror British Dinghy Heliograph 4inch 1943.jpg

English: This British 1940s 4"x4" stainless steel mirror with attached foresight wand and cloth sachet case is an example of those commonly issued in British emergency kits in World War II. They were developed in 1942-1943 so that downed pilots could signal to rescue planes and ships with reflected sunlight. Such emergency mirrors are more likely to be termed "signal mirrors" or "emergency signaling mirrors" in non-Commonwealth countries, or if they lack a foresight. Signal mirrors are required lifeboat equipment in most countries, and are provided in the survival kits of most military pilots. Both the mirror and the painted wand are 14 gauge steel. The mirror has a 1/4" diameter sighting hole, countersunk from the rear and painted black to reduce reflections. The foresight has a 7/8" diameter head with a 3/16" diameter sighting hole. The case has separate pockets for the mirror and the wand. The user held the wand in front of the mirror, and sighted the target by looking through the rear of the mirror sighting hole and the wand sighting hole. The user then centered the shadow of the mirror sighting hole on the foresight hole, with the aid of the shadows cast by the scribed mirror lines on the foresight, by tilting the mirror. When the target was centered in the two sighting holes, and the shadow of the mirror hole was centered on the foresight hole, the mirror reflected sunlight on the target. The prototype of this mirror, and probably this mirror as well, was made by George Ibberson & Company General Machinists, 146 West Street, Sheffield 1. The testing of the prototype is described in the Report "Heliograph mirrors for emergency dinghies", Report No. , issued 28 February 1943 by the Marine Aircraft Experimental Establishment, Helensburgh. That report is in the British National Archives, cataloged under AVIA 19/218 at http://www.nationalarchives.gov.uk/catalogue/displaycataloguedetails.asp?CATLN=6&CATID=3074923&j=1