I received several blocks of these core planes many years ago. I broke them up into 1/2" squares, put them in 8x magnifying bug boxes and sold them for quite a while on eBay. The blocks contained 12 planes each, bolted together at each corner like a loaf of bread. The planes contain 32x32 cores (bits) each, in a 5"x5" frame (see the picture.) Each core was about the size of a poppy seed, but had 5 wires going through it (2 horizontal, 2 vertical and 1 diagonal.) I believe computers moved from core to transistor memory around 1965, and then progressed to the semiconductor stage. Here's a picture of the plane, and a couple of blow-ups. Thought you might enjoy it.