Exact age is unknown, but does look Victorian rather than QEII era. We’ve seen these types of FOBS before, though in slightly different designs with all being Victorian from the mid to late 1800s. Made of a gold plated metal, possibly pinchbeck it measures 30mm wide x 30mm high ex the round link & weighs 7.3 grams. There are no noticeable makers marks or hallmarks. The back gives the impression it opens up, but it doesn’t.