Beautiful brass c clasp brooch. Most likely Eastern European. The flower bud in this piece looks like glass but doesn’t feel like glass, I’m guessing it’s an early celluloid made to mimic swirl glass.
If you don’t know much avoids celluloid, bakelite, acrylic, etc this is a very comprehensive article:
https://chatsworthlady.com/2012/06/21/vintage-plastic-jewelry-what-it-is-and-isnt/