see the Online Encyclopedia of Silver Marks, Hallmarks & Maker's Marks
As I see so many mistakes in listings of Dutch Silver I shortly explain Dutch Silvermarks
90 is often called a Hallmark or Sterling Silver but it stands for silverplated, as well as 100
the logo DE or DE are the initials of the tea and coffee factory Douwe Egberts in Joure (Fr) Holland and the articles with this are often marked HH 90 which stands for Hooikaas, Schoonhoven and silverplated
a Dutch silver article should at least have a hallmark and a makersmark
I've seen listings with 15th, 16th or 17th Century silver, while the Hallmarks clearly indicate it is made after 1800
you can find Hallmarks and Silvermarks on the above mentioned Encyclopedia
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