The pound sign is, at heart, a fancy letter L. It descends from an ornate capital L standing for the Latin libra, the Roman balance scale and the unit of weight it measured. The connection to weighing is not incidental but foundational: before it counted money, the libra counted heaviness, the amount of a thing that would balance the scale. The elegant loop and crossbar of the modern symbol are the flourishes that time and calligraphy added to that plain initial, dressing up an L until it became the mark we know.

What gives the character its quiet depth is a family resemblance hiding in plain sight. That same libra is the source of lb, the everyday abbreviation for pounds of weight. So the currency symbol and the weight abbreviation are not distant cousins but siblings, two descendants of a single Roman word, one branch drifting toward money and the other staying with mass. Whenever you write lb on a parcel or the pound sign before a price, you are using two different shorthands for the same ancient term, split apart by centuries but sharing one root. The crossbar on the currency symbol, meanwhile, is itself an old abbreviation mark, the traditional way of signalling that a letter has been shortened, a small stroke that says this L stands in for a longer word.

The exhibit can even point to the symbol in the wild at a precise moment. The Bank of England Museum holds a cheque dated 7 January 1661, and on it the pound sign appears clearly discernible, doing exactly the job it still does now, marking a sum of money in a document of trade. There is something steadying about that. The mark has been in continuous, recognisable service for well over three centuries, and its shape reaches back further still, to a Roman scale weighing goods rather than counting coin. In one ornate letter, the pound sign holds together weight and wealth, ancient Rome and a seventeenth-century cheque, all balanced on the memory of a single word.