"Maltese Cross" and non standard sizes from factory?

I has a '71 440 HP engine that had a maltese cross with an X beside it on the front pad, and when i opened it up to refresh it and measured everything, #2 main bearings were 0.010" overersize and the rest were std.
I put it back together with the proper bearings and had to buy one that was 0.010'' for #2 and the clearances checked out perfectly.
My machinist said the crank was perfect with no taper or out of round when i took it in to be polished but he wanted to grind the crank 0.010'' on all of the mains and i insisted on leaving it alone.
I ran that engine after that for years without any problems.

O.P.:
I haven't seen that stamping on a block before, so i don't know what it means.