silver lidded urn by Hjertzell Olof Gunnar

I have acquired this lidded urn which I think mat be Swedish in origin but I am unsure as to whether the markings are for Silver or Silver Plate.  The lid and the main body are marked . I would welcome any assistance.

I think it's Swedish sterling silver but I'm no expert

if it's heavy it may well be plate

Thank you both, it is very light and there is no tang to taste

The three crowns are the Swedish national mark (equal to the lion passant), the S is for silver standard. The odd figure on the right will be the town mark. You're missing the date stamp, which should be a letter followed by a number.
https://www.925-1000.com/Fsweden_Date_Code.html

Town mark is for Stockholm, and the maker's mark is for Hjertzell Olof Gunnar, 1933-1945.
http://www.silvercollection.it/DICTIONARYEUHALLMARKSWEDEN.HTML

Thank you all so much , you are all so helpful and I really appreciate it