It is an overprint used in North Sumatra by the Republic of Indonesia in the period 1945 to 1949. My catalogue isn't any more explicit about this, except that all stamps in stock were overprinted. The underlying stamp is from the Japanese occupation during WWII.
Jan
Think this is the answer for PTT
http://www.wikiwand.com/en/Pos_Indonesia
re: JAPAN with P.T.T. cancel
It is an overprint used in North Sumatra by the Republic of Indonesia in the period 1945 to 1949. My catalogue isn't any more explicit about this, except that all stamps in stock were overprinted. The underlying stamp is from the Japanese occupation during WWII.
Jan
re: JAPAN with P.T.T. cancel
Think this is the answer for PTT
http://www.wikiwand.com/en/Pos_Indonesia