Complex sentence: The earliest pots were predominantly used for olive oil, mainly from Baetica, and because the maker's seal and other notes (e.g. tituli picti) are still available on the fragments they are a rich primary source for understanding Roman commerce.
Split into simpler sentences: The earliest pots were predominantly used for oil, mainly from Baetica. Because the maker's seals and other notes (e.g. tituli picti) are still available on the fragments, they are a rich primary source for understanding Roman commerce.