Hi Sedgewick - I believe the numbers indicate metic, six point sockets, which I am sure you have figured out The xm is a year code that MAC used to represent the years 1997 and 1998.
Hope you find this of some help.
36 Chevy 1.5 ton - rusting away 52 Chevy 3100 - in progress 72 Chevy K20 - DD
The xm is a year code that MAC used to represent the years 1997 and 1998.