In 2012, he began designing the Legacy Machine Perpetual, a 581-component watch with his revised perpetual calendar option – which didn’t work. “I was driven mad by the clockwork,” Mr. McDonnell said, “and it was excruciating, I was in pieces.”
By 2014 Mr McDonnell had returned to Belfast and started assembling a prototype of the design. “It was a disaster,” he said. “Absolutely catastrophic. The day change mechanism did not work. But then, one Monday morning, he was back on his bench, “and the solution fell from the sky! It was so simple and elegant – only one small lever was needed, an extension of an existing lever.
The Legacy Machine Perpetual was introduced in 2015 in two versions, red gold for 138,000 Swiss francs ($147,590) or platinum for 168,000 Swiss francs. And the following year, it won the Grand Prix d’Horlogerie de Genève in the calendar watch category.
“It was Stephen’s revolution in the history of watchmaking,” said Mr. Büsser. The watch, one of MB&F’s best sellers, sold over 250 pieces and “none came back with a perpetual calendar issue”, he added.
Last year MB&F introduced the Legacy Machine Perpetual EVO, a sportier version of the original; there’s a three-year waiting list, Büsser said.
Mr McDonnell, who has worked occasionally for other brands but is not authorized to name them, is now collaborating with MB&F on “something new and very complicated”, he said, which is to be released more late this year. “They give me complete carte blanche,” he said. “It’s wonderful, but it’s also terrifying. I don’t know how many watches I have left in me.