The 2-cent Hamilton Bank Note Issue (Scott 21) has a red frame and black portrait of Fernandez de Cordoba, a Spanish conquistador who played a prominent part in Spain's conquest of Central America and who was one of the men responsible for the selection of the original site of Panama City in 1519.
This stamp is quite scarce compared to others in this series. As such, it has an interesting history: originally 20,000 were overprinted at the ICC Administration Building in Panama City in October 1906. However, on the next month's printing the overprints read down (Scott 23), so to make sure there were enough for collectors an additional 30,000 were printed with the overprint reading up. Even so, this pales in comparison with the 2,370,000 of the Overprint Reading down variety.
The earliest recorded use of this stamp is dated October 29, 1906. The 2-cent Hamilton was intended to be used on domestic letters and foreign postcards. It is easily found in unused condition but on cover or postcard it is much scarcer. In combination with other stamps it is even scarcer.