unknown item

I bought this item at an auction. Trying to find out what it is and if it might be worth anything. On the back it says derby silver co quadruple plate in a cicrle around a anchor above a crown. Above the circle it says pat may 23 1905 then right below that it has a number 7. Below the circle it is stamped 1776. I have been trying to research this on the internet and not having much luck would appreciate any help in this.