Incredibly rare 'Raid Block' number 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. The raid block itself was normally positioned at the head of the plotting path and provided information such as strength, height and whether the aircraft were 'hostile', 'friendly' or 'unknown'. This number '21' is printed on some form of early plastic and measures approximately 37 x 22mm. It would have been positioned on the raid block along with other tiles representing height, raid serial number and so on. Please note you are buying one single number tile, other numbers, the block and map etc. are shown for illustrative purposes only. Note also that the tile is not a perfect fit on the raid block shown and may have been used with a different one (various styles exist to our knowledge). We have a small quantity of numbers available. A fantastic opportunity to create a small Operations room display. If you are lucky enough to own a Sector clock then this is a must have item. Stock code M21700l.