The Rand currency was introduced in the then Union of South Africa on 14 February 1961, shortly before the establishment of the Republic on 31 May 1961. It had a two-and-a-half-cent denomination, replacing the earlier threepence coin which had the same mass and dimensions. The new coins were 50% silver and retained the reverse design of the threepence created in 1925 by George Kruger Gray, featuring a Protea flower.
The 2 1/2 cents circulating denomination was short-lived though, and was discontinued after 1964 in favour of a new 2 cents coin.
In 1997, the South African Mint started issuing Non-Circulating Legal Tender (NCLT) 2 1/2 cents coins in a new series known - from the flower featuring on the coin - as the Protea coin series; the flower is now on the obverse, and the reverse designs celebrate various aspects of South African heritage and nature. The coins are usually issued in a "Crown and tickey" set (tickey being the nickname of the coin), together with a Crown piece (one ounce silver), with new themes every year.
The composition is Sterling Silver - 92.% silver alloyed with 7.5% copper.
This coin 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 2018 South African Inventions theme features Computed Tomography (CT), invented by Allan McLeod Cormack. The CT is an imaging procedure that uses special X-ray equipment to create detailed pictures or scans of areas inside the body. It is also termed computerised tomography and computerised axial tomography (CAT). It uses computer-processed combinations of many X-ray measurements taken from different angles to produce cross-sectional (tomographic) images (virtual "slices") of specific areas of a scanned object, allowing the user to see inside the object without cutting. The 1979 Nobel Prize in Physiology or Medicine was awarded jointly to South African American physicist Allan M. Cormack and British electrical engineer Godfrey N. Hounsfield "for the development of computer assisted tomography."