When it comes to making coins with different production techniques, the Portuguese State Mint has been an innovator in recent years.

Following a special coin in 2014 that featured a gold inlay against a silver planchet, the Portuguese State Mint in 2015 is issuing a single Proof gold and silver €2.5 coin that has connected parts, with half of the coin composed of gold and the other half of silver.

Two gold nodules are adjacent to three silver sections, the yin of gold connected with the yang of silver. In a way, these shapes mimic the five rings of the Olympic logo.

The coin celebrates the 2016 Summer Olympic Games in Rio de Janeiro, Brazil. In addition to the precious metals version, an Uncirculated copper-nickel version with the same designs is also being produced.

The .999 fine gold and silver coin weighs 14.85 grams and measures 28 millimeters in diameter. It has a mintage limit of 28,000 pieces.

The copper-nickel coin weighs 10 grams, measures 28 millimeters in diameter and has a mintage limit of 150,000 pieces.

Because these are Olympic coin issues, and the United States Olympic Committee is protective of licensees selling Olympic-themed memorabilia, even currency of other nations, collectors in the United States will have to search the secondary market for these pieces.