Scientific examination of classic Spanish stamps with colour error, a non-invasive micro-Raman and micro-XRF approach: The King Alfonso XIII (1889–1901 “Pelón”) 15 cents definitive issue

A complete Raman and X-ray fluorescence study on the Spanish 15 cents stamp from the King Alfonso XIII (1889–1901) issue with colour error is presented. Even though this fact has been known since 1890, there is no record of such error in any catalogue. The number of printed stamps was around 1300 million, and it is believed that around 4000 stamps were printed with colour error, but less than 100 stamps are known to have survived. The official colour of the 15 cents stamp was chestnut-brown violet, but due to the long period of time in which this stamp was used and due to the different printings, the differences in colour are common. All the stamps with colour error considered in this study present the same philatelic and printing technical characteristics as the standard stamps, but with chestnut-brown orange or yellow shades. As a result of the scientific analysis, the differences of the colour lie only in the use of different kinds of inks. The nature of the inks as well as the way this error happened is discussed, discarding the presence of fakes or forgeries in the stamps analysed.