My mum gave me her silver cup that she was given at her christening in 1940. There are four marks on the bottom of the cup - the three towers (1937), the maker's mark of Grann & Laglye and the assay mark for Johannes Siggaard. Unfortunately, I have no clue what the forth mark at the bottom of the picture is. Any ideas what it is? My thanks in advance.

- the marks

- the cup