Leroy 01

Historical significance

• Commissioned by the Portuguese collector Antonio Augusto de Carvalho Monteiro with instructions to combine everything then achievable in watchmaking science and mechanics, the Leroy 01 held a long-standing reputation, repeated in specialist literature, as the most complicated watch in the world for roughly eight decades after its completion. [1](http://www.mdt.besancon.fr/wp-content/uploads/2014/07/La-Leroy-01_fiche-%C3%A9l%C3%A8ve.pdf)
• The watch has two dials (one on each face) carrying 24 functions in total, including a display of the time in 125 cities, a perpetual calendar, and interchangeable star charts, contained within a 71 mm case — an unusually large but still pocket-portable form for the number of functions included. [1](http://www.mdt.besancon.fr/wp-content/uploads/2014/07/La-Leroy-01_fiche-%C3%A9l%C3%A8ve.pdf)
• Remained in the Carvalho Monteiro family until 1953, when it was acquired by public subscription for the city of Besançon's museum; researchers should treat claims about its 'most complicated' status as a period and specialist-literature characterisation rather than a fixed, permanently unchallengeable record, since later watches (including modern grande complications) have since matched or exceeded its complication count by some counts.

Sources & references

1. Musée du Temps, Besançon, published catalogue materials on the Leroy 01
2. hautehorlogerie.org, Fondation de la Haute Horlogerie, encyclopedia entry on Louis Leroy

Where sources disagree, the disagreement is stated rather than resolved silently.