The letters in the squares, are they E P N S? If so that would be electroplated nickel sliver. They often used to put it in fancy lettering to make it look like a high-end silver date lettering system. I think your cup is a baby cup, usually a gift for a newborn child or at the child's christening. If you run a search for silver baby cup lots of them come up. They used to be a very popular gift and would often be engraved with the baby's name, birthdate or initials. My brother got one as a baby from our great-grandmother. She gave me a silver porringer when I was born and I still have it.
