|
Rim (coin)
The rim of a coin is the raised part of the coin that completely encircles the perimeter on both obverse and reverse sides. Not to be confused with the edge of the coin, which is also known as its "third side". This is the part which exceeds the area of the die which strikes the coin during production, and as a result is pushed upward and sharpened to form a sort of border around the coin's design. The raised rim reduces wear on the face of the coin. For accessibility purposes, the rim of the coin is sometimes milled with certain patterns in order for the blind to more easily distinguish between coins. The Australian two dollar coin has periodically distributed around its edge a short set of grooves, which alternate between the smooth rim, whilst the one dollar coin has a larger set of grooves, and the similar-sized ten cent coin has grooves continuously about its edge. See also * Milled coinage In numismatics, the term milled coinage (also known as machine-struck coin ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Coin
A coin is a small, flat (usually depending on the country or value), round piece of metal or plastic used primarily as a medium of exchange or legal tender. They are standardized in weight, and produced in large quantities at a mint in order to facilitate trade. They are most often issued by a government. Coins often have images, numerals, or text on them. ''Obverse'' and its opposite, ''reverse'', refer to the two flat faces of coins and medals. In this usage, ''obverse'' means the front face of the object and ''reverse'' means the back face. The obverse of a coin is commonly called ''heads'', because it often depicts the head of a prominent person, and the reverse ''tails''. Coins are usually made of metal or an alloy, or sometimes of man-made materials. They are usually disc shaped. Coins, made of valuable metal, are stored in large quantities as bullion coins. Other coins are used as money in everyday transactions, circulating alongside banknotes. Usually the highest va ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Milling (machining)
Milling is the process of machining using rotary Milling cutter, cutters to remove material by advancing a cutter into a workpiece. This may be done by varying direction on one or several axes, cutter head speed, and pressure. Milling covers a wide variety of different operations and machines, on scales from small individual parts to large, heavy-duty gang milling operations. It is one of the most commonly used processes for machining custom parts to precise tolerances. Milling can be done with a wide range of machine tools. The original class of machine tools for milling was the milling machine (often called a mill). After the advent of computer numerical control (CNC) in the 1960s, milling machines evolved into ''machining centers'': milling machines augmented by automatic tool changers, tool magazines or carousels, CNC capability, coolant systems, and enclosures. Milling centers are generally classified as vertical machining centers (VMCs) or horizontal machining centers (HMCs) ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Blindness
Visual impairment, also known as vision impairment, is a medical definition primarily measured based on an individual's better eye visual acuity; in the absence of treatment such as correctable eyewear, assistive devices, and medical treatment– visual impairment may cause the individual difficulties with normal daily tasks including reading and walking. Low vision is a functional definition of visual impairment that is chronic, uncorrectable with treatment or correctable lenses, and impacts daily living. As such low vision can be used as a disability metric and varies based on an individual's experience, environmental demands, accommodations, and access to services. The American Academy of Ophthalmology defines visual impairment as the best-corrected visual acuity of less than 20/40 in the better eye, and the World Health Organization defines it as a presenting acuity of less than 6/12 in the better eye. The term blindness is used for complete or nearly complete vision loss. In ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Australian Two Dollar Coin
The Australian two-dollar coin is the highest-denomination coin of the Australian dollar. It was first issued on 20 June 1988, having been in planning since the mid-1970s. It replaced the Australian two-dollar note due to having a longer circulatory life. The only "mint set only" year was 1991. $2 coins are legal tender for amounts not exceeding 10 times the face value of the coin for any payment of a debt. Design In accordance with all other Australian coins, the obverse features the portrait of the reigning monarch, who during the lifetime of the coin has only been Queen Elizabeth II. From 1988 to 1998 the portrait of her was by Raphael Maklouf before being replaced in the following year by one sculpted by Ian Rank-Broadley. Since 2019, the effigy of Elizabeth II by artist Jody Clark has been released into circulation. Designed by Horst Hahne, the reverse depicts an Aboriginal Elder, a Walpiri-Anmatyerre man of the Northern Territory of Australia, inspired by an Ainslie Rob ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Australian One Dollar Coin
The Australian one-dollar coin is the second most valuable circulation denomination coin of the Australian dollar after the two-dollar coin; there are also non-circulating legal-tender coins of higher denominations (five-, ten-, two-hundred-dollar coins and the one-million-dollar coin). It was first issued on 14 May 1984 to replace the one-dollar note which was then in circulation, although plans to introduce a dollar coin had existed since the mid-1970s. The first year of minting saw 186.3 million of the coins produced at the Royal Australian Mint in Canberra. Four portraits of Queen Elizabeth II have featured on the obverse, the 1984 head of Queen Elizabeth II by Arnold Machin; between 1985 and 1998, the head by Raphael Maklouf; between 1999 and 2009, the head by Ian Rank-Broadley; and since 2019, the effigy of Elizabeth II by artist Jody Clark has been released into circulation. The coin features an inscription on its obverse of AUSTRALIA on the right-hand side and ELIZA ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Australian Ten-cent Coin
The Australian ten-cent coin is a coin of the decimal Australian dollar. When the dollar was introduced as half of an Australian pound on 14 February 1966, the coin inherited the specifications of the pre-decimal shilling; both coins were worth one twentieth of a pound and were called "bob". On introduction it was the fourth-lowest denomination coin. Since the withdrawal from circulation of the one and two cent coins in 1992, it has been the second-lowest denomination coin in circulation. For the first year of minting (1966), 30 million coins were produced at the British Royal Mint (then in London), and 11 million at the Royal Australian Mint in Canberra. Since then, all coins have been produced in Canberra, with the exception of 1981 when 40 million coins from the Royal Mint's new headquarters in Llantrisant, Wales supplemented the 76.1 million produced in Canberra. Years without issue for the 10c, were 1986, 1987, 1995 and 1996. Those years were only for mint and proof sets. ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Milled Coinage
In numismatics, the term milled coinage (also known as machine-struck coinage) is used to describe coins which are produced by some form of machine, rather than by manually hammering coin blanks between two dies (hammered coinage) or casting coins from dies. Introduction Until 1550, coinage techniques used in European mints had not progressed from the hammered coinage of Ancient Greece. This was problematic because an increase in the supply of bullion from central Europe and America was overworking mints. That led to low quality coins which were easily forged or clipped, i.e. precious metal was shaved from the edges of the coins. In accordance with Gresham's law, the clipped and forged coins drove good coins out of circulation, depreciating the currency. Leonardo da Vinci's notebooks showed there was a better way and Donato Bramante, the architect who made the initial plans for St. Peter's Basilica, developed a screw press to make the lead bullae attached to Papal document ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
