Japanese Occupation, NJ1-NJ5. Single frame Kanji overprint on Postage Due stamps, 1942. Forged overprint: George P. Coulter, “Malaya: From Singapore Northward: The Single-Frame Kanji Overprints”, Japanese Philately, Vol. 21 (February 1966): 3-16. Robson Lowe (editor), The Gee-Ma Forgeries, p.10. Description of genuine chops: James M. Gallatly, “The Japanese Single-Lined Chops of Malaya”, The Philatelist, Vol. 23 (March 1957): 147-51; James M. Gallatly, “The Malayan Chops: Dates of Overprinting”, The Philatelist, Vol. 23 (June 1957): 235-38.