Hi Ringo, I think it is Geneva. If there is a 3 on top of the head, it is 800/1000 silver. Look Tardy 5th edition english language (2005 reprint) p. 394. Regards silverfan
"Weltliches Silber 2", the inventory of the Swiss National Museum in Zürich, is usally a reliable source. It attributes the mark to Julien Derriey, (1812-1865). The fork should be dated around 1850 or a bit later.