Silvertone metal, adjustable length. OLD Bakelite whistle on silvertone chain. Could be an old policeman's whistle. The ball inside the whistle is made of cork. Push in clasp set with a red glass bead.
Fancy brass caps around the drop and the round beads.
Unsure of what type of plastic this is, but it does have seams so it is not bakelite. The O rings are really dark, don't know if they are supposed to be this way or not. There is a chip on the back of the pendant, but it can not be seen from the front and doesn't detract from the appearance. Very difficult to depict in the photos. Faux I think.