This is a slip-top spoon which was probably made from 1650-1697. Unfortunately, the date letter is very worn and so I need to identify the maker to stand a better chance of dating accurately. The initials are surrounded by dots and the second one is almost certainly an L; the first could be a T, but I'm not sure.
I've finally found a possibility for this spoon: Jeremiah Lee of London who entered his mark in 1728 (Grimwade 1466). This really is much later than the style of the spoon would suggest, but the others marks agree with the date.