Brooch Art Deco period 1920 to 1940

Mourning jewellery from the Art Deco period 1920 to 1940 - Probably Swedish mourning brooch (Three Crowns hallmark?) with inlays of jet (gagat) and in silver setting (hallmark 935S); very beautifully worked; on the outer sides small chips (see photos), but not really disturbing; pin works; traces of use according to age (see photos); dimensions: approx. 1 x 3.5 cm / 3.85 g