josstrom is absolutely right! Although this particular mark is very blurry, it depicts Saint Erik, Stockholm's and Sweden's patron saint. He was king of Sweden, killed in Uppsala (which was the capital at this time) in 1160 by the Danish prince and his soldiers. According to the legend, a spring began to flow from where his head fell. His relics are kept in the cathedral in Uppsala. In the 14th century he became patron saint of Stockholm.
I can also add that your bowl is made for serving sauce.