Bazeries cylinder
A cylinder cipher with about twenty rotating disks, described by the French cryptanalyst Étienne Bazeries.
Étienne Bazeries (1846–1931) was a French army officer and cryptanalyst. He published his work on cylinder ciphers in Les Chiffres secrets dévoilés (1901). The idea resembles the wheel Thomas Jefferson drew up in the 1790s, but here the disks sit on a shared axle, each with a scrambled alphabet, and the key is the order of the disks.
The sender sets the disks according to the key, writes the plaintext along one row, and sends a different row as the ciphertext. With about twenty disks there are more possible orderings than anyone could test by hand.