this looks like a czech stamped metal filigree style pin. it would have had a glass stone in the middle at one point. it might be from the 20s or 30s given its patina, although these metal stampings are still made today.
the most prized antique ones are found as parts of elaborate necklaces with colorful glass. a brooch like yours, given its condition and missing stone, probably doesn't have much value--a few dollars. i have a couple similar pieces in my shop that are in good condition and i have a hard time getting more than $20.
