TOP ROW
 

Compotus, Writings , c 1495, Paris or Basle.
 
Compotus, Writings , c 1488 perhaps Lyons.
 
anon. c1540
 
 
The Harmonic Hand of Guido D'Arezzo, Sacerdotale Juxta S.Romanae Ecclesiae , Venice Petri Rabani 1554. This is also known as the GUIDONIAN HAND.

Here is another example from Wollick's Opus Aureum Musice... Cologne 1504.
 
Hugo's Flores musice artis, Strassburg, 1488
Jehan Tabourot, Compot et Manuel Calendrier par lequel toutes personnes peuvent facilement apprendre et scavoir les Cours du Soleil & de la Lune , Jean Richer, Paris, 1588. The twelve months of the year fastened to joints of the fingers.

from Petit Copost en Francoys ,printed in Paris in 1530.
 
remembering the letters of the alphabet
 
Anianus, Compotus cum commento , Lyons, 1488
 
from the T'Ung Shu
an ancient Chinese almanac. The hand is marked with the hours of the day and from the markings can be divined the best date for a decision or when an event will happen. It is also possible to tell if a tic in the eyelid is lucky or not.