A rare silver keyless mystery watch, Armand Schwob & frère, 'Mystérieuse', no. 142 circa 1890

crescent-shaped frosted gilt cylinder escapement , flat rimmed three arm balance, hands moved by rotating glass discs with Arabic numerals, outer minute track, silver case glazed on both sides, engine turning to the cuvette, cuvette signed A.S. & F. and numbered 142.