I’m old enough that when I went to secondary school we used those!
Some time during my first year the maths teacher bought one of the first electronic calculators, four function (add, subtract, multiply, divide) and using Reverse Polish Notation, it cost £200! This was in 1970/1 when the average salary was somewhere in the £2000 region.
We had them at school in the 60s. My last year of primary school was spent down in Oxfordshire and the primary school had 3 new Curtas!
While you’re searching the junk shops if you find an old science lab set of scales buy them if the weight set is included, the value of the little bits of platinum used for the tiny weights is remarkably high.