In 1777 Amsterdam has used a damaged town town which comes close to your spoon (image above), including the standard mark and year letter S. See below:
The maker's mark you are showing of Voet is for; Jacobus Buth maker's mark a flounder, registered in Amsterdam 1690-1749 (deceased). I got him in my collection:
We also have the Amsterdam silversmith Andries Vis, registered 1741-1799 maker's mark a fish. I have him in my collection.
I show you the back of the spoon:
Both spoon of Andries Vis and Jacobus Buth have an assay grove. Andries Vis and Jacobus Buth were known makers of cast spoons
Could you give me the exact weight and length of your spoon?