I notice that the 24c issue of 1861-1868 gives a lot of buyers and sellers problems when it comes to identifying the numerous color varieties! I see common color varieties being confused with the scarce more...
The Stamp Specialist H. L. Lindquist published this series of 20 books in 1940-8. Typically there are seven to eleven topics per book of assembled articles about philately. The books are now classified by...