Hi everyone, long time reader, first time poster over here.
I'm from Belgium, and I think I might be able to help out.
The three stars in the triangle is the mark of the Belgium firm Wolfers Frères, named after the three brothers who took over their father's business in the 1890's. Around 1892 the three star mark was introduced. By then they had already been awarded the title of 'Court-supplier', and it became, together with the firm of Delheid, the biggest silver producer in Belgium. The firm itself was enormously succesful and sold their silver in their own shops, but they also supplied the most renowned firms in Germany, the Netherlands, and even Cartier in France.
One of the brothers, Philippe Wolfers would even become a fine jeweller working in Art Nouveau-style, the likes of Lalique, you must defenitely google his work, it is extraordinary!
Now for the other marks:
the crescent and crown is indeed the German silver hallmark, and it is known that at the height of the Wolfers' firms popularity, they contracted other firms in Germany and France, to produce their designs and supply them, to keep up whith the demand. So most likely it was produced by the firm of K. Steenaerts in Germany to supply Wolfers.
Hope this helps, and sorry for the long story!
Edit; after some searching I found it's not K. Steenaerts, but H. Steenaerts, it stands for Heinrich Steenaerts, a jeweller and silversmith in Aachen, Germany, he was born in 1860 and died in 1925, and also was 'Hofjuwelier', meaning he was jeweller and supplier to the court. Here's the link to his obituary card:
https://www.wgff-tz.de/details.php?id=218944
