This article & links explains hallmarks & assay offices: https://www.antiquestradegazette.com/guides/information-guides/hallmarks/
A lot of electroplated items have stamps which can be confused with hallmarks: look out for EPNS 'electro-plated nickel silver'. From what I can see googling 'Kenson silver', this seems to have been an American firm which specialised in reproduction antique EPNS.
Geoffrey. I have googled "Kenson Silver". Can find an Indian company, plastics Co, books, kids toys, anything else but silver. It may be an Australian company as an item is mentioned in Trove which is the National library of Australia. I've contacted them and awaiting reply
Elaine, if you google Kenson EPNS you will find many examples for sale around the world. Where source and timing are mentioned it seems that most people believe it was a british company , almost all say Vintage, that is less than 100 years old. The most commonly repeated era seems to be 1940s and many items are stamped with the word reproduction
Dave