RAF operations room plaque '4'

Unusual plaque believed to have been used in RAF Filter and Sector Operations Rooms during the Battle of Britain and beyond to display important information relating to the strength of an enemy raid.  This relatively crude triangular shaped acetate plaque measures approximately 25 x 50mm, is black, with the number '4' hand-painted in white on one side.  It came in with other similar plaques and operations room pieces.  A fantastic opportunity to create a small operations room display.  Stock code M26757.

NB. Map not included.