Silver spoon marked with Dutch sword (19th century version), mark 9C I believe as I can see a thin separation line between 9 and C, and possibly the mark JSS in a cursive font.
Hi, it could be Groningen, ninth alphabet C for circa 1807, maker's mark not clear. The double date letter and maker's mark to indicate high silver purity. No access to my library till the end of next week.
I looked in my book "zilvermerken van voet" and it's there as you say. I am still getting to know the book and city marks.
Using the date and city name you provided I was able to pin down the makers mark to "Johannes Warren" and find the same marks on the web: https://keuren.zilver.nl/iw/geen-categorie/