Ten famous explorers

Sporrongs series "Ten Famous Explorers" was issued in 1973, in Platinum, Gold, Silver and Bronse. 

The artist, Kauko Räsänen (1926–2015) was a prominent Finnish sculptor and medal artist known for his abstract expression. He created both large-scale public sculptures and monuments and was also a skilled medal artist. Räsänen’s work is characterized by a modern, stylized form that draws on abstract elements, and he used various materials and techniques to achieve his unique, often monumental-like pieces. His decoration of Helsinki City Hall in 1967 is one of his best-known public works, and his creations can be found in several urban spaces across Finland. His education at the Finnish Academy of Fine Arts helped shape his distinctive style and contribution to Finnish contemporary art.

The bronze medals was patinated in black. Compared to the more clean silver medals, it can be debated if it was a sucsess or not. It depends probably on taste. In my opinion the dark patina helps accentuating the medals sculptural caracter.

Bronze and silver medals react differently to patination processes, and this can affect their aesthetic appeal and durability. Patinating bronze involves creating a dark surface finish by accelerating oxidation, often resulting in a rich, dark brown or black patina. While this can enhance the depth and texture of a design, bronze’s copper content can sometimes lead to uneven coloration or a slightly "muddy" appearance, especially with darker finishes. Additionally, bronze patinas may be less stable over time, potentially fading or developing unwanted greenish spots (verdigris) with exposure to air and humidity.

In contrast, silver medals achieve patination through controlled tarnishing that results in a subtle, often bluish-gray surface. This effect can enhance details without obscuring the design, creating a refined, even look. Silver patinas also tend to remain stable and uniform, as silver tarnishes more predictably than bronze oxidizes. Thus, patinated silver medals are often perceived as more successful in maintaining both visual appeal and surface integrity over time compared to patinated bronze medals, which can sometimes be less consistent and harder to control.