core 'revision' number...BS? BUSTED!!

Member is selling a very early 340 cast block, 6/22/67. This would make it a very early casting. It has been said the suffix after the casting number (-4) may be a 4th core 'revision' and everyone is hard up on the -1 blocks being the best or thickest or having the least core shift. I don't back that theory. I personally think the blocks were cast 8 at a time in 8 boxes and possibly with 8 cores. The -x is the core or the position and is used in QC to identify what core or position it was cast in to identify casting faults, not to rank the block. Any believers?

Note the 4 in the casting number.on such an early date casting, that doesn't support the core revision number theory but does support the 8 cores cast at once and this one was just in cavity 4
Wow! They could pour 8 at a time??? Krazzzyyyy!!
What exactly is Core-Shift tho? and how would you know if you had a Shifted one?