9-16. Sexegenary Overprints, 1897. Forged overprints. Two Fournier forged overprints on remainders and 15 other fakes: J.A.C. Farmer, Leeward Islands Philately 1897 Sexagenary Overprint And Its Forgeries, (the author, Aldershot, Hunts, England, 1988). Forged overprint and Specimen cancellation (hand stamped “Ultramar”): The Encyclopedia of British Empire Postage Stamps 1661-1947, Vol. VI, p.204. Forged overprint: Jerold M. Holmes, “Clues To The Sexagenary Overprint Forgeries”, Stamp Collecting, Vol. 88 (May 17, 1957): 318. Fournier and another forged overprint: The Serrane Guide/ Stamp Forgeries of the World to 1926, p.214.
Genuine and forged postmarks and revenue cancellations of high value KGVI large Key Type stamps: Eric Yendall, The King George VI Large Key Type Revenue and Postage High Value Stamps, 1937-53 (The Royal Philatelic Society, London, 2008), pp.158-60.