Marks on a letter opener from the Nijmegen 4 day walk in Hol

I am new here and normally only collect coins. I have today received a letter opener that refers to the annual 4 day walk/march to Nijmegen.

I believe that it is probably silver plate and there are 3 marks on it that I don’t understand.

I have attached an image of the marks, the last one I think is either 90 or 9C.

If anybody can help it would be much appreciated

I think you are correct in suggesting it is silver plate. “90” is an often-used number in plating and refers to the amount of silver used to plate a standard set of items. For an explanation see here. I can’t help with the other marks.