This William Sumner salt spoon was assayed in London in 1804-1805. JB has also been punched onto the handle near the hallmarks. If this is a journeyman's tally mark, then it is unusual in that it is so large, and also it is well away from the maker's mark. If it is a second maker's mark (James Beebe?) then it is unusual in that it does not overstamp the first. And an owner's initials were usually not punched but engraved.
So what does the JB mark mean? Please let me know if you have any ideas.