The top box is either a KR 550 or 650. 550 is the older one with no ball bearing slides. On the 650 the full width drawers are ball bearing slides, the small drawers are friction slides. The 550 was made from roughly late '70s to mid '80s, 650 replaced it. I have one of each, both are great boxes.
The bottom boxes look older, late '70s KR 557 I think. It's not wide enough to fully fit the top box on. All friction slides.