Most of those strange little stampings were either to mark sets ( like left & right case halves ) or clearences.
Remember A 7 & 10 predate modern machining tools so every time a part was machined the tool got shorter.
Semi automatic lathes moved a set distance unlike modern computer controlled machines that cut to a pre determined size.
Machined parts were tested with go no-go type gauges and stamped according to the results so that tollerances could be maintained within acceptable limits.
You notice this when you try to put a bitsa together where a part like say a mainshaft is a good fit in a box with a u/s layshaft but a really bad fit in the box that you are trying to rebuild.
I personally have had all sorts or grief with things like boxes that would not turn because these is no running clearences when they a re bolted together but the various bit worked well in their donor cases.
