Quarter farthing Quarter farthing The British quarter farthing (d) coin was a unit of currency equaling one sixteenth of a penny ( of a pound sterling). It was produced for circulation in Ceylon in various years between 1839 and 1853, with proof coins being produced in 1868. It is the smallest denomination of pound sterling coin ever minted. The coin is considered to be part of British coinage because it has no indication of what country it was minted for, being made in the same style as the contemporary half-farthing which was legal tender in Britain between 1842 and 1869. Before Decimal
Penny graph are the coin graphs formed from unit circles. If each vertex is represented by a point the center of its circle, then two vertices will be adjacent if and only if their distance is the minimum distance among all pairs of points. Therefore, penny graphs have also been called minimum-distance graphs, smallest-distance graphs, or closest-pairs graphs. Similarly, in a mutual nearest neighbor graph that links pairs of points in the plane that are each other's nearest neighbors, each connected component is a penny graph, although edges in different components may have different lengths. Every penny graph is a unit disk