For dressing the inclined impulse surface of the escape teeth.
Crom, HST, page 443, describes this as Vallet's improvement, circa 1820, on the the original tool by LeNormand, and is shown in Foucher's Manuel d'Horlogerie of 1850, plate 4. Brass body, steel escape wheel mounting. Height 11 cm.
A rare tool with some light corrosion showing on the steel, but generally in very good original condition.
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