Acorn BBC Micro Model A

The cheap Beeb: 16K of memory, no printer or analogue ports fitted, and the expectation that a school would upgrade it later. Most were, which is why the Model A is markedly scarcer than the B despite being sold alongside it — an unmodified one, with the empty sockets still empty, is the find. Otherwise identical hardware, so it demonstrates Acorn's design intent: one board, sold at two prices, with the difference in what is fitted.