A clever little invention that was on display at the Industries Exhibition at Birmingham in 1886. It was made by the Birmingham silversmiths G.E. Walton & Co.
Looks like an anti-theft devise, if a pickpocket pulled on the chain, those little spikes would drop down to catch the pocket fabric, the owner would know to pull it out while holding the spikes flat...
Described as 'Chief Inspector William's Patent Watch Protector or Thief Catcher', it presumably had the duel benefit of preventing the actual theft and also that of alerting the victim to the attempt and thus possibly leading to the apprehension of the culprit.