K+E had a big facility not far from my home back in the 60s -- I still have a warm spot in my heart for slide rules, kennyc. I've still got one. I had fun showing it to the kids when they were in high school.
When I was 6, in first grade, we used an abacus in class to help learn beginning math concepts, Stitchawl -- I remember it helping. I was surprised when my kids' started school and they didn't use them. So, I went out and bought one. Just a plastic one, but it got the concepts across. It was especially good at demonstrating simple multiplication.