Art Nouveau Bar Pin Glass 900 Silver Rhinestones C Clasp Vintage Antique? Quaint

This is a sweet 1 1/2" long and 3/4" high bar pin that swirls around the various colored glass rhinestones with the flow of art nouveau. It has a c clasp which can be one indicator of earlier jewelry and what looks to me like a T bar at the other end of the fastener. If so ( and I am just a beginner) that is another indicator of its age. It responded positive for silver on an 18k acid test, but with an average response, which makes me think it is silver plated. 900 is still silver, just not 925 sterling. There are a lot of small, clear and inverted stones and what appears like a tiny bit of marcasite.