Rare Vintage Micro Mosaic Carved Bone Brooch

Rare old vintage micro mosaic brooch, likely from the 1940's or possibly earlier. This features an intricate floral mosaic with tones of vivid blue contrasted with red, white, yellow and green. Centred in a carved bone brooch with functional brass c-clasp. There is a faint stamp on the back, which I believe to be in Hebrew although I cannot entirely read what it says. Very good vintage condition--general signs of wear.