Numbering system changes after class A1-52164 as the consecutive class
numbers (01-164) are replaced with the actual class number for the given year.
Example for years 1952 - 1977: A1-6523A
A1 = Primary school or "A" school
65 = Year 1965
23 = Class number
(When large classes were split in two either A (Alpha), B (Bravo) or P (Port), S (Starboard) were appended to the class number.