1906 post card to London with a 1d cancelled by a superb strike of the extremely rare KOSTERFONTEIN 21 JUN 06 canceller. Kosterfontein was a farm in the Rustenburg District, the farm owner was Jan Hendrik Grobler, a 35 year old Boer soldier who had surrendered to the British at Rustenburg on 26 September 1900 and was interred in the Middleburg Camp for the duration of the Boer War. Putzel in his book on the Postmarks of South Africa states that no postmark had been seen from Kosterfontein !! A superb and extremely rare card.