My piece of pottery is marked on the bottom with “Calif” or “California” and a number, but no maker’s name. Is it rare / old / valuable?
Not necessarily. (Unfortunately, this is the most common answer you will find in the FAQs.) Just because a piece is marked with “California” doesn’t mean it is old or vintage. It can be from a completely modern company. But it could also be a newer piece from a company that produced pottery for many years. Confusingly, it can even be from a company NOT from California! There is no perfect rule when it comes to pottery.