Thank you! These dishes have an history! 😉
Once in Pisa we had only terracotta dishes, without glaze. The first objects with transparent glaze appeared between 1000 and 1300 when Pisa was trading with the Mediterranean countries. They were used by rich people on their tables, but the new bowls were placed on the facades of the churches too, and now we can see them (their copies, the orignal are into the museum San Matteo of Pisa). They were decorated with geometric motifs (Arabic ones) or motifs that had to do with the sea (boats and fish) or with Christian symbols. If you are interested look here: https://it.wikipedia.org/wiki/Bacini_ceramici_delle_chiese_pisane