a blast from the post:, page-7

Cuisenaire rod
Set of coloured number rods created by Belgian primary school teacher Georges Cuisenaire (1891-1976).

I spent my high school holidays working in a factory that made these. Factory bought 9 cement mixers to colour them...dye/paint in mixer and let them tumble around for awhile. Then they were sent to homes in bulk containers where hosewives would pack them into the green plastic boxes ready for sale.

Cheers