Shallow Stoneware Bowl Incised Mark

I'd be very grateful if anyone can help to identify the maker of this bowl. It is a shallow footed bowl approximately 22cm in diameter. On the bottom towards the rim of the foot are some incised markings. The first seems to me to be intertwined letters, either S B or S P maybe ; and then to the right of this there are maybe numbers - 54? - or further letters. I'm wondering if this is maybe a hobbyist potter, as the marks seem rather uncertain. Any help appreciated!

Those black dots on the clay base are quite common on French pottery.

I never knew that.....thank you!