This lovely piece of 1920's Art Deco is something we don't see too often.
A black and white enamelled Deco styled case, there are some missing pieces of enamel especially around the clasp. A little catch which on pulling slightly flips open the front of the watch, to reveal a tiny mirror set in the lid and the watch dial. Which for 100 years old is as clean as a whistle.
The watch is working cannot ascertain what movement it is but would suspect a Jewelled lever Swiss Movement.