The book Merken van Friese goud- en zilversmeden
Today's authority on Frisian silversmiths is Mr. Jan Schipper of http://www.zilverstudie.nl
Jan Schipper does extending research on Frisian silver, the (hall) marks & silversmiths with outstanding results and new findings. Unfortunately for us the site is for selected members only.
I have discussed your spoon with Mr. Jan Schipper and he wrote me the maker's mark is unknown to him.
Indeed your spoon could be early 18th century, looking at the images. You have the spoon in hand and are the best to judge.