We haven't seen this style of spoon before, but it is a interesting design. A '13' stamp on silver indicates it's 81.25% pure silver, a measure of purity used in the Lothig system, used in a number of European countries in the 18th and 19th centuries. The mark represents 13/16ths of a unit of purity, which is a historical standard. It is probably German, mid-late nineteenth century. It is in great condition.
Hallmarked '13' 'WURMBERG'
It measures 22cm long and weighs 47 grams.