So pretty -- and they do look later don't they? Always confusing with such timeless and classic designs.
The coating that you see on the exposed threads is celluloid, and the brooch itself looks 30's/40's with a heat applied pinback. The flowers themselves are unusually 'new' looking I agree, but from the pics, it seems that they are original (maybe if you check closely, you can see if the piece has been modified in any way).