"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, an engineering innovation developed in East London 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. Its obverse features the coat of arms of South Africa, the year ‘2016’ and the words ‘South Africa’ in all the official languages. The reverse of the 2-½ cent tickey shows a single dolos with the denomination ‘2-½ c’ while the obverse features the words ‘South Africa’ with the year ‘2016’ and -a Protea.
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.
Eric Mowbray Merrifield, East London Harbour Engineer from 1961 to 1976, is credited with the invention of the dolos, but in the late 1990s Aubrey Kruger, Merrifield’s young draughtsman at the time, claimed that he and Merrifield considered the shape of the concrete blocks together to be used in the protection of East London’s extensive breakwaters following damage done by a major storm in 1963.
Although Merrifield died in 1982 and Kruger’s claim cannot be settled either way, the focus in celebrating this engineering feat is not on the inventor, but on the origins of the invention- South Africa. The dolos has changed the face of coastlines around the world."- SA Mint