So, what do I have ?

[Patrick Chadwick]

There is a misprint!

It is obviously supposed to list the markings, going round clockwise, taking the manufacturing code as 0 degrees.
So the sequence should be 0, 90, 180, 270 (not 240).
Check: the numbers 1,19 etc are indeed at 180 degrees to the manuf. code.

They are batch numbers. Go here for a detailed explanation:


A guide to headstamps