法國，47 x 33 mm，約 1810
French, 47 x 33 mm, circa 1810
An extremely rare watch key with integrated foldable miniature opera glass
Case: gilt and granulated brass case set with blue stones. Central lens, surrounded by mother-of-pearl with gleaming polished steel flowerets.
Illustrated and described in: "The Keys of Time" by Yves Droz, France 2012, p. 104-105.