Travellers to these islands mentioned that gold coinage was in use on the coasts, but not inland.
The major cultural influence on these islands was Indic, first Hindu, then Buddhist. Buddhism came to Srivijaya by year 425. Srivijayan kings dominated the region through trade and conquest throughout the 7th-9th centuries. the kingdom helped spread the Malay culture throughout Sumatra, Malay Peninsula, and western Borneo. Srivijaya influence waned in the 11th century. The island was then subject to conquests from Javanese kingdoms, first Singhasari and subsequently Majapahit. At the same time, Islam made its way to the Aceh region of Sumatra, spreading through contacts with Arabs and Indian traders. By the late 13th century, the monarch of Samudra kingdom (in Aceh) was converted to Islam.