Hi Leo,
Please check for other little marks, so far you are showing Dutch fantasy/pseudo marks. Do I see a little dolphin mark near the center point? I believe so.
The Dutch dolphin mark; the 1859 duty mark for new unguaranteed objects of national origin. This mark was used on all new silver objects below legal standard of fineness, those with non-precious metal additions, and on new heavily gold or silver plated objects, as long as the average precious metal content after melting with the base metal was at least 250/1000. It was also struck on rejected objects which had been submitted at lowest standard of fineness. In that case the maker had to choose between destruction or unguaranteed marking. This mark was sometimes also mistakenly used on old and foreign objects. Dolphin mark used from 1859-1893 and valid from 1859 till 1953.
For more information about Dutch (hall)marks see:
viewtopic.php?f=5&t=32028Oel.