The King of Spain once harvested pearls from the oyster beds of Mexico.
Kino seems to enjoy the legacy of harvesting pearls from the same beds that made the King of Spain rich and powerful.
This was the bed that had raised the King of Spain to be a great power in Europe in past years, had helped to pay for his wars, and had decorated the churches for his soul's sake. (ch 2)
Kino knows how pearls are from sand that irritates the oyster over time. He considers finding a pearl lucky, because the bottom of the oyster bed is “strewn with shells of broken, opened oysters.” Oysters are a gift from God.
It is interesting that Steinbeck tells us about the King of Spain, who influenced Mexico if only by taking its wealth and contributing nothing to its inhabitants like Kino. The King of Spain got rich, Spain got powerful, and Mexico got nothing but a legacy of exploitation.