Hi, welcome to the forum.
I believe it to be pseudo or fantasy marks, please check for other marks. Around 1860 antique silver with old silver marks were in high demand due to world wide silver exhibitions and America and the UK did not charge import duty for silver over 100 years old, thus Dutch silversmiths got creative and made silver with an "antique" look including fantasy or pseudo marks. Pseudo or fantasy marks are still used today.
For Dutch (hall)marks see:
http://www.925-1000.com/forum/viewtopic.php?f=5&t=32028
Oel.