Sometimes, very rarely, we have a pleasure of discovering an unpublished manuscript. Over the past years, Antiquorum has been entrusted with many very important Breguet documents and, in this very sale, papers of the well-known Louis Cottier.Here we have a document of equal importance, which has been prepared for publication by the author. It is a major treatise on escapements, beautifully handwritten, with superbly done hand-colored drawings. It covers all the basic forms of escapements but also describes and illustrates the constant force escapement, Breguet tourbillon, detent, etc.It also illustrates such mechanisms as the wandering hour display, independent seconds driven from a single barrel, repetition for musical watches, half-quarter repetition (found for instance in the rare Patek Philippe watch, lot. No. 347), calculation for an equation of time cam, fusee with maintaining power, etc...The manuscript shows very skillful draftsmanship, resulting in a rare combination of beauty and technical clarity. The text shows deep knowledge of the subject. It was no doubt destined for an exhibition and later for publication.In 1897, Ecole de Cluses exhibited at the Exposition du Centenaire de l'horlogerie at Besançon. There, they displayed a large group of escapements. Millard, writing in "L'Union horlogère" considered their exhibit to be without equal. The present manuscript, which no doubt accompanied the exhibit, was a descriptive document concerning their escapements.The Cluses school exhibited again at the 1900 Paris Exposition, winning the highest prize; Lavaivre himself was awarded a gold medal.Levaivre, who attended the Ecole d'horlogerie de Cluses, successively became a professor there, then director of the school, and finally President. After his marriage to a woman from Chamonix, he moved to that city, of which he later became mayor. He contributed two major publications to the field of horology, one on clocks and the other on watches. The present book is his most important technical work.