Silver Crown 2016 Dolos, Coin from South Africa - detailed information

South Africa pioneered modern bullion coinage when it first issued the Krugerrand on 3 July 1967 to help market South African gold; it is the first modern bullion coin and is still issued today.

Gradually, the South African Mint started diversifying the range, first by issuing fractional Krugerrands, then by introducing different designs and metals, such as a silver one-ounce (1 oz) format. These include silver 1 oz Krugerrands, the Protea series, the Natura series, as well as one-year types that do not fall into a particular series. Some are made of Sterling silver (92.5%) alloyed with copper, just like the British pre-decimal Crown coins, and some are 99.9% silver. The Sterling versions are overall heavier though, so they also contain exactly one ounce of pure silver or 1oz Absolute Silver Weight (1.000 oz ASW); they are called "Crowns" in the "Crown and Tickey" coin sets in which some of them are issued, and are officially denominated as two, five or ten Rands.

This coin, denominated as Two Rands (R 2) is part of the Crown and Tickey series of South African coins issued with different themes every year by the South African Mint to celebrate South Africa’s history and achievements.

The R2 Crown and Tickey were first introduced in 1997, and in 2016 a new theme entitled South African Inventions was adapted. The first invention to be featured in this new theme is the dolos (plural: dolosse), an engineering innovation developed in East London (a town in the South Africa) in 1963 to protect harbour walls and dissipate the energy of breaking waves. The dolos’ design ensures that these concrete boulders form an interlocking yet porous wall.

The reverse of the R2 crown depicts people on a harbour wall protected by a number of dolosse. A dolos can weigh up to 20 tons, thus they are placed in position and on top of each other by cranes, and over time, tend to get further entangled as they are shifted by the waves of the ocean. Roughly 10,000 dolosse are required to preserve a kilometre of coastline and so they are found in their millions along coastlines worldwide.

These un-reinforced concrete shapes are manufactured by pouring concrete into a steel mould. The concrete is sometimes mixed with steel fibres to strengthen the dolosse in the absence of reinforcing. Construction of the dolosse takes place as close as possible to the area where they will be placed due to their great mass and difficulty in moving them. They are often numbered so that their movement can be monitored over time and so that engineers can gauge if more dolosse need to be added to the pile. The dolos has changed the face of coastlines around the world.