It loooks like Carl Valdemar Sørensen Hillerød (Denmark) born 1834 working 1855 His own business 18th february 1859 - 1879. If he is the silver smith - then the engraving must be at a later date. perhaps when he was born.
This swan was used in the 16th and 17th century in Zwickau (DDR part of Germany) Now yuor item is not 17th century - but it gives you a place to start searching.
I think that it is Swedish. Could you describe the marks. Or try a better picture. The stripe zig zag is called "oldermands ranke" when they controlled the silver they took a sample before stamping the silver. The silver smith had given his mark but before the official mark was giver they took this ...
And it is very common to put the guardein mark and the 3 towers. 3 towers is the city mark of Copenhagen used sinse 1608 but from 1893 the 3 towers coyuld be used all over Denmark. And at the same time it became up to the silver smith whether he wanted to use the mark.