The silver coins issued by the Guptas were actually called "Rupaka" (option 1).

Option 2, Karshapana, is not the correct answer because this was a coin used in ancient India primarily in the Maurya Empire and was made of various metals, typically copper or silver.

Option 3, Dinara, is not the correct answer. Although the Gupta Empire did issue coins known as the Dinara, these were usually made of gold, not silver.

Lastly, Option 4, Pana, is incorrect because Pana was a unit of currency used in ancient India but was not specific to the Gupta Empire or their silver coins.

The silver coins issued by the Gupta Empire were thus most accurately known as Rupaka. The term "Rupaka," in general, is used to depict something that is in form or image, hence used by the Gupta empire for their detailed and artistically crafted silver coinage.