Based on the technique and materials, this is likely an Italian antique micromosaic pendant top (most likely from the 1920s). It's a delicate piece created using the traditional technique of placing tiny glass pieces one by one. There's a worn marking on the back that's difficult to make out, but it may read "ITALY." It weighs 10g and is a rhombus shape with sides of 2.5cm. The craftsmanship is quite detailed, suggesting it's a quality item. However, the brass on the back shows signs of aging. While the mosaic on the front has no chips and is in good condition for an antique, it's an old item that has been stored at my grandmother's house for many years, so please consider this when purchasing.