In 2017 I walked the Camino Portuguese from Porto to Santiago (interior route).
Just outside Porto, I stayed the first night at the Albergue de Pelegrinos, SRa da Hora (Via Portus Cale).CI031505107
My first sello for that Camino was hand-painted. They had little pen/brushes, and the hospitaleros/hospitaleras handmade each stamp for each person (all similar, if not identical). Beautiful, memorable, and the one I remember the most.
In general, I think the stamps and credentials create a wonderful memento of the whole experience, my most treasured souvenir of all.
I was always taken by how creative and proud people are of their stamps. Once, close to Santiago, an elderly woman came out of her house and called me over to stamp my credential, lovely. Thanks for the memory!