What was the term ‘Tankas’ used for in medieval society?

NCERT (2026-27): “7. Women … For instance, slaves were openly sold in markets, like any other commodity, and were regularly exchanged as gifts. When Ibn Battuta reached Sind he purchased ‘horses, camels and slaves’ as gifts for Sultan Muhammad bin Tughlaq. When he reached Multan, he presented the governor with, ‘a slave and horse together with raisins and almonds’. Muhammad bin Tughlaq, informs Ibn Battuta, was so happy with the sermon of a preacher named Nasiruddin that he gave him ‘a hundred thousand tankas (coins) and two hundred slaves’.…”