831572-A is referenced by 3 patents.

831,572. Date indicators. SINGLETON, J. S. March 17, 1958 [July 3, 1957], No. 21019/57. Class 106 (4). A date indicator comprises a pair of cubes each face of which bears a zero or a single numeral so distributed between the faces that any number from one to thirty-one can be displayed. The cubes may be made of wood, plastic or metal, they may be solid or hollow and may be formed by folding suitable blanks. One arrangement of numerals is shown in Figs. 2 and 3 wherein one symbol can represent 6 or 9. Another cube can be used to display day names using one symbol to represent M or W. Instead of numerals dots may be arranged on the faces as in dominoes and one zero would have to give place to nine dots as 6 and 9 would need a face each.

Title
Improvements in and relating to perpetual calendar devices
Application Number
GB19570021019 19570703
Publication Number
831572 (A)
Application Date
July 3, 1957
Publication Date
March 30, 1960
Assignee
John Stephenson Singleton
IPC
G09D 03/00
G09D 03/02
View Original Source Download PDF