The Old Physics Lesson

The subject of this month’s installment of Retronics is a small brownish suitcase which, when first opened (Figure 1), took me back instantly to physics classes about 30 years ago, in particular those aimed at teaching me the principles of electricity and magnetism.
The suitcase was shown to me by a retired classroom assistant who had kept it in safe storage for more years that he could remember. In fact, he had two of these suitcases, one incomplete, the other, complete, unused and in pristine condition as shown here.