With due respect. This topic has been discussed before. In general you are right if we are talking about silver worldwide. Unmarked legal silver exists but is uncommon. This spoon is, however, most likely European made. In Europe there are very little unmarked silver produced. What unmarked silver you can find is very old objects, private orders (e.g. court suppliers), folk jewellery, medical instruments and some other rather rare objects and of course coins. There is hardly any reason why any maker would not mark his work unless it is made in illegal below standard fineness. He might get caught! Makers are honest and proud people. They like to "advertise: I made this, I'm a good skilled goldsmith" by marking the object they made. Anyway, the probability that this spoon is silver is close to nil. The probability it being plated is 99%.
Have the spoon tested the way Peter suggested but not with acid and you will know is it silver or not. Secondly, all Scandinavian countries have very strict legislation on how to mark silver, forget Scandinavia.