Can't really help with any useful information, unfortunately - other than to suggest that it looks more like a perfume dispenser of some description than a decanter. Put a little CIF or Brasso, or some proprietary metal polish on your handkerchief, and rub the metalwork - if there is any silver present then you should end up with a very black mark on your hanky. If this was a piece of some quality i.e. a silver collar, then I would have expected some hall/silver content marks. You can also sometimes smell silver, a slightly sharp metalic aroma - no black mark, then no silver. Regret this is not of much use. Where did you acquire this - antique market, charity shop, Christmas gift..........do you have reason to believe this might originate from some particular country (don't know where you are)
