The series is printed by photo-offset in softback format but to very high quality.
The run was limited again to 150 softback sets.
The original publications were in an unusual format (15 cm x 7 cm softback pictorial).
Approximately 150 softback copies were produced of each year from 1864 to 1878 and made available either as part of a set or as singles.
A less expensive binding method is that used for paperback books (sometimes called softback or softcover).
Collected volumes have also been produced as both hardback and softback books.
From the 33rd (1896) edition onwards hardback copies became available at twice the price of the softback.
As of early 2014, softback and hardback editions up to and including 1946 have been published.
