Just a little something to add to Bahner excellent answer:
The first mark is as mentioned the maker's mark. The second is the city mark for Stockholm, a crowned king with long hair, St. Erik.
The three crowns is of course the Swedish control mark, since 1913 used together with S for silver, and I9 is correctly 1959.
These are all the marks that was mandatory on silver from 1754 until July 1988.
The mark GVH on the other side could be a designers mark, or simply stating that it was manufactured by Guldvaruhuset, "The Gold Department Store", in Stockholm which has this mark registered 1923- 1965.
Pendant like this where very popular in Sweden in the '50s, and you can find them with lots of different stones, and small variations.
P.S. I myself find the date mark chart on this site a little hard to interpret, I'm used to reading it like this:
http://www.oscarianska.se/arsbokstaver/" onclick="window.open(this.href);return false;