The official unit of currency in Panama is the Balboa. The value of the Balboa is pegged to the US Dollar at a rate of 1:1, so 1 Balboa = 1 USD.
In fact the two currencies are so closely linked that Panama doesn't produce any of it's own bank notes, and paper US Dollars are used here as currency. A 1 Balboa coin was introduced in 2011 by the current government, and is very commonly referred to as a "Martinelli", after the current president, Ricardo Martinelli. The 1 Balboa coin is actually minted by the Royal Canadian Mint, chosen because they already have experience of minting bi-metallic coins. (The Canadian "toonie" $2 coin is very similar to the Balboa coin)
The Balboa is broken down into 100 sub-units, just as the US Dollar is. Here the cents are called centesimos, or often colloquially as centavos. US coins are accepted everywhere, although Panama does have it's own set of coins too. These aren't accepted back in the US, so sort your pocket change when heading north!
As well as the "Martinelli" there is a 50c coin, and the rest of the set that will be familiar to North Americans - 25c, 10c, 5c, 1c. These are all the same size and weights as the US versions.
The gentleman depicted on the coins is Vasco Núñez de Balboa.
From Wikipedia - "Vasco Núñez de Balboa (c. 1475 – around January 12–21, 1519) was a Spanish explorer, governor, and conquistador. He is best known for having crossed the Isthmus of Panama to the Pacific Ocean in 1513, becoming the first European to lead an expedition to have seen or reached the Pacific from the New World."
One of my friends once made me laugh when I showed him one of the Panamanian coins. "I bet he was sat on a horse when he had that photo taken!"
Señor Balboa has had his name attributed to many things in Panama. There can't be a town in Panama without at least one road or street carrying his name. He has quite a few statues erected in his honour too. He even has a port town and a district named after him. Further afield he has appeared in the lyrics of a Randy Newman song ("The Great Nations of Europe") and even has a lunar crater named after him - now that really is having your name live on long after you have died.
To add further potential confusion to Panamanian conversation and transactions, one of the national beers is also named after the ubiquitous Señor Balboa:-
"Bring ten Balboa to the meeting on Friday night!"