Scott 2011 Standard Postage Stamp Catalogue, Vol. 6: Countries of the World- San-Z

Almost 15,000 value changes were recorded in Volume 6, which now includes listings and values for Countries of the World San Marino through Z. The country with most value changes is Venezuela, with more than 4,100 changes. More than 1,700 value changes were recorded for Turkey, many of them concentrated in the 1950s and later issues. Other countries with significant changes include; Togo, South Africa, Sierra Leone, Spanish Guinea, Spanish Morocco and Uganda.