They are part numbers.
My car, built in early 65, has the same numbers.
Sorry for the poor picture quality, but you should get the idea...

Attached Images
000_0574.jpg (405.76 KB, 73 downloads)
crosshead_part_number
000_0575.jpg (387.3 KB, 73 downloads)
crosshead_part_number2
Last edited by musew; 22/11/15 02:37 PM. Reason: edit 2