RAF filter room plotting counter '5'

Incredibly rare Filter Room Plotting 'Counter' used to display important information relating to an enemy raid.  When details of aircraft were received at Group Filter Room level, the information was interpreted on a map table.  Diamond shaped counters like this were produced in seven colours.  Manufactured in an early plastic, approximately 1.5cm x 1.5cm, green with the number '5' in white to obverse.  Filter Room plotting equipment is even rarer to find than that of Operations Rooms.  Discovered at the Filter Room of RAF Watnall, Headquarters of 12 Group Fighter Command during WW2.  We have literally a handful of such items, most of which we are keeping.  Excellent condition.  Stock code M26537.