The Kingdom of Keoland has its own currency, with which you are each quite familiar. It consists of the three coins: the Lion, or "cub" (the copper piece), the Seal (the silver piece), and the Eagle (the gold piece).
The ancestors of the royal family were seafarers far away, at the ocean, and the royal crest still contains a seal. Accordingly, the base silver coin depicts and is called a "Seal."
The grandfather of the current king was a progressive, and he wanted to make sure that even the most humble commoner would have a bit of the regal in his life. Thus, the "Lion" was born: a copper coin worth a tenth of a seal with a proud lion on it. However, because they are worth so little, these coins have come to be referred to by the peasantry as "cubs."
If you are so fortunate as to amass wealth enough, you are familiar with the Eagle, which is depicted on the gold coin of Keoland. While people often deal with larger amounts than a single seal, most common folk do not carry around as large a denomination as an eagle; instead, they carry around multiple seals (think of them as like $100 bills - most people in the US don't carry a bunch of 100-dollar bills around, instead getting 10s and 20s from the ATM).