While there were a couple of firms in Israel and Portugal who printed a few of the issues of Biafra and some commemorative sets issued between 1963 and 1965, these comprise only a very small number of Nigeria's stamps. So we can ignore them for the purposes of this discussion, since familiarity with their work is only essential to understanding the specific issues that they produced, rather than Nigerian philately as a whole. By and large, nearly all stamps issued for Nigeria and its component colonies, since 1874 have been printed by six firms, four of which were based in the UK:
1. Thomas De La Rue and Co., and its Belgian subsidiary Delrieu.
2. Waterlow and Sons Ltd.
3. Bradbury Wilkinson
4. Harrison and Sons
5. Nigerian Security Printing and Minting Company (NSP&M)
6. Jon Enschede and sons of the Netherlands.
I will discuss the general characteristics of each printer' work with respect to:
- Printing process
- Paper employed
- Inks used and use of shades to identify printings
- Other characteristics used to identify printings
- Gum used
- The introduction of chalk-surfacing to the paper used for most intermediate and high-value denominations. Generally speaking, these were any stamps above those required to pay postcard, printed matter and local letter rates. The introduction of this paper generally started in 1905 and there was more than one type of chalk-surfacing, although Gibbons generally only lists one type. I have seen thin papers with a thin chalk coating, as well as very thick papers with a thick, opaque white chalky coating similar to the Dickinson coated paper found on the 6d Edward VII issue of Great Britain printed by Somerset House in 1913.
- The introduction of coloured papers and papers that had a different colour on the surface and a different colour on the back. There were four basic colours used: green, yellow, red and blue. These will be discussed in detail in another post, but the surface and back colours of these stamps varied greatly and is a very useful aid in identifying printings. These papers continued in use well into the multiple script period.
- The true purple colour is a deep and dull purple, which is not bright in any way. When first soaked, the ink will become bright purple and then will fade into very pale purple with prolonged exposure. When used on chalky paper, the fading can be so pronounced that it almost appears as if the ink is missing.
- The true green colour is a deep and dull green. When first exposed to moisture it becomes a bright blue green, fades with prolonged exposure to yellow-green and then finally to a bright greenish yellow.