The Leroy Chronograph

The enemy of every fine watch in 1913 was invisible: magnetism, seeping from the new century's dynamos, motors and electric lines, quietly ruining balance springs. Louis Leroy had patented his defence years earlier, and this chronograph carries it, the whole movement enclosed in the firm's anti-magnetic screen, an armour most makers never attempted. The inner cover is stamped for the patent, and a copy of the 1906 patent document travels with the watch.

Around that idea Leroy built a chronograph of real grandeur: 18ct gold, 51.9mm, 106.9 grams, with a flawless white enamel dial signed Leroy Paris, slim Arabic numerals, an outer fifths-of-a-second track, an instantaneous sixty-minute register at twelve and running seconds at six, read against rose gold poire hands with the chronograph work in blued steel. The chronograph works through the crown, starting, stopping and returning to zero without hesitation, and the watch winds, sets and runs cleanly.

The house behind it was the most decorated French maker of its day, and this piece shows the workshop at full stretch: a column-wheel movement finished in gilt with ruby jewels in gold chatons, sealed inside its screen like an instrument in its case.

And the watch is documented to the day. Leroy's own ledger records it, names its first owner and the Paris street he lived on, and prices the sale in the francs of the summer of 1913; the entry is set out in The Archive below. The gold shows only light hairlines from a century of careful carrying, the crystal is sound and the crown secure.

The marks, the movement and the condition are set out piece by piece in the drawers below; the ledger entry and the patent are set out in The Archive.