Hi burchard,
The crown mark was used between 1807 and 1812 in Holland under the reign of Louis Napolean (brother of Boneparte).
However somethings don't match:
- the crown is a poor knock off (can be due to wear and tear, or due to forgery)
- the sword mark was not used till the Bonapartes were gone and never used for restamping.
- the sword is a poor knock off as well
- the only town using a key mark is Leiden and this is not one of them (so must be a makers mark)
- the style is not according to date (which doesn't say all)
I did a quick search and found no maker that matches the "key" mark, only a pseudo mark (445 Citroen - Valse silvermerken in Nederland).
So my conclusion: A late 19th century piece with pseudo marks (but nice pseudo marks).
Hope that helped.
.