I know I must be misreading this, are you saying that, although Snap-On tool boxes cost many thousands of dollars, and in today's dollars always have, SOME OF THE DRAWERS DO NOT HAVE BALL BEARING SLIDES?? WTF?
It's SO. I'd say it's early 90's or older 761 box by the drawer count and the lack of barrel or "freezer key" style of locks and solid casters. I had a 761 I bought new around 96 that I'm pretty sure had all those changes and the 1001 shop box the boss bought new in 95 after I started there.