I distinctly remember a class set of grey calculators. Like a box of 30. I'm not sure if we had a box in each class or the box moved around to the class using them, I just remember them appearing on some days. In general we weren't allowed to use them for maths but on occasion they would bring them out and we'd do... something, I can't actually remember. They weren't scientific ones, just plain +-*/ ones. This would have been primary school in the 90s.