Obverse and reverse in the context of Loonie

The Serdi were a Celtic tribe inhabiting Thrace. They were located around Serdica (Bulgarian: Сердика, romanized: Serdika; Latin: Ulpia Serdica; Greek: Σαρδική o Σαρδῶν πόλις, romanized: Sardike o Sardon polis), now Sofia in Bulgaria, which reflects their ethnonym. They would have established themselves in this area during the Celtic migrations at the end of the 4th century BC, though there is no evidence of their existence before the 1st century BC. Serdi are among traditional tribal names reported into the Roman era. They were gradually Thracianized over the centuries but retained their Celtic character in material culture up to a late date. According to other sources they may have been simply of Thracian origin; according to others they may have been of mixed Thraco-Celtic origin.

A coin is a small object, usually round and flat, 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. The faces of coins or medals are sometimes called the obverse and the reverse, referring to the front and back sides, respectively. The obverse of a coin is commonly called heads, because it often depicts the head of a prominent person, and the reverse is known as tails.

The first metal coins – invented in the ancient Greek world and disseminated during the Hellenistic period – were precious metal–based, and were invented in order to simplify and regularize the task of measuring and weighing bullion (bulk metal) carried around for the purpose of transactions. They carried their value within the coins themselves, but the stampings also induced manipulations, such as the clipping of coins to remove some of the precious metal.

The Naqsh-e Jahan Square (Persian: میدان نقش جهان, romanized: Maidān-e Naqsh-e Jahān, lit. 'Image of the World Square'), also known as the Shah Square (میدان شاه) prior to 1979, and sometimes known as the Imam Square, is a square situated at the center of Isfahan, Iran. Constructed between 1598 and 1629, it is now an important historical site, and one of UNESCO's World Heritage Sites. It is 160 metres (520 ft) wide by 560 metres (1,840 ft) long – an area of 89,600 square metres (964,000 sq ft). The square is surrounded by buildings from the Safavid era. The Shah Mosque is situated on the south side of this square. On the west side is the Ali Qapu Palace. Sheikh Lotfollah Mosque is situated on the eastern side of this square and at the northern side Qeysarie Gate opens into the Isfahan Grand Bazaar. Today, Namaaz-e Jom'eh (the Muslim Friday prayer) is held in the Shah Mosque.

The square is depicted on the reverse of the Iranian 20,000 rials banknote. Stores are owned by trust of Ostandari Isfahan.

The Morgan dollar is a United States dollar coin minted from 1878 to 1904, in 1921, and beginning again in 2021 as a collectible. It was the first standard silver dollar minted since the passage of the Coinage Act of 1873, which ended the free coining of silver and the production of the previous design, the Seated Liberty dollar. It contained 412.5 Troy grains of 90% pure silver (or 371.25 Troy grains = 24.057 g; 0.7734 ozt of pure silver). The coin is named after its designer, United States Mint Assistant Engraver George T. Morgan. The obverse depicts a profile portrait representing Liberty, modeled by Anna Willess Williams, while the reverse depicts an eagle with wings outstretched. The mint mark, if present, appears on the reverse above between D and O in "Dollar".

The dollar was authorized by the Bland–Allison Act. Following the passage of the 1873 act, mining interests lobbied to restore free silver, which would require the Mint to accept all silver presented to it and return it, struck into coin. Instead, the Bland–Allison Act was passed, which required the Treasury to purchase between two and four million dollars' worth of silver at market value to be coined into dollars each month. In 1890, the Bland–Allison Act was repealed by the Sherman Silver Purchase Act, which required the Treasury to purchase 4,500,000 troy ounces (140,000 kg) of silver each month, but only required further silver dollar production for one year. This act, once again, was repealed in 1893.

The Dutch East India Company (Dutch: Vereenigde Oostindische Compagnie, often known as VOC) was a chartered company which issued a considerable series of coinage in bronze, silver and gold for its territories in the Far East between 1602 and 1799.

In Greek mythology, Strymon (/stryˈmɔːn/; Ancient Greek: Στρυμών) was a river-god and son of the Titans Oceanus and his sister-wife Tethys. He was a king of Thrace. By the Muses, Euterpe or Calliope or Terpsichore, he became the father of Rhesus. His other sons were Olynthus and Brangas.

Neaera bore Strymon's daughter, Evadne who became the wife of King Argus. He was also the father of Tereine who mothered Thrassa by the god Ares. Another daughter, Rhodope became the mother of Athos by Poseidon.

Coinage of the Ptolemaic kingdom was struck in Phoenician weight, also known as Ptolemaic weight (about 14.2 grams) which was the weight of a Ptolemaic tetradrachm. This standard, which was not used elsewhere in the Hellenistic world, was smaller than the dominant Attic weight (about 17.28 grams) which was the weight of standard Hellenistic tetradrachm. Consequentially, Ptolemaic coins are smaller than other Hellenistic coinage. In terms of art, the coins, which were made of silver, followed the example set by contemporary Greek currencies, with dynastic figures being typically portrayed. The Ptolemaic coin making process often resulted in a central depression, similar to what can be found on Seleucid coinage.

The Ptolemaic dynasty introduced standard coinage to Egypt, where pre-existing native dynasties made only very limited use of coins. Egyptian gold stater was the first coin ever minted in ancient Egypt around 360 BC during the reign of pharaoh Teos of the 30th Dynasty. These coins were used to pay salaries of Greek mercenaries in his service.

There are eight euro coin denominations, ranging from one cent to two euro (the euro is divided into a hundred cents). The coins first came into use in 2002. They have a common reverse, portraying a map of Europe, but each country in the eurozone has its own design on the obverse, which means that each coin has a variety of different designs in circulation at once. Four European microstates that are not members of the European Union (Andorra, Monaco, San Marino, and Vatican City) use the euro as their currency and also have the right to mint coins with their own designs on the obverse side.

The coins, and various commemorative coins, are minted at numerous national mints across the eurozone to strict national quotas. Not every eurozone member state has its own mint. Obverse designs are chosen nationally, while the reverse and the currency as a whole is managed by the European Central Bank (ECB).

The United States ten-dollar bill (US$10) is a denomination of U.S. currency. The obverse of the bill features the portrait of Alexander Hamilton, who served as the first U.S. secretary of the treasury, two renditions of the torch of the Statue of Liberty (Liberty Enlightening the World), and the words "We the People" from the original engrossed preamble of the United States Constitution. The reverse features the U.S. Treasury Building. All $10 bills issued today are Federal Reserve Notes.

As of December 2018, the average life of a $10 bill in circulation is 5.3 years before it is replaced due to wear. Ten-dollar bills are delivered by Federal Reserve Banks bound with yellow straps.

The United States one-dollar bill (US$1), sometimes referred to as a single, has been the lowest value denomination of United States paper currency since the discontinuation of U.S. fractional currency notes in 1876. An image of the first U.S. president (1789–1797), George Washington, based on the Athenaeum Portrait, a 1796 painting by Gilbert Stuart, is currently featured on the obverse, and the Great Seal of the United States is featured on the reverse. The one-dollar bill has the oldest overall design of all U.S. currency currently in use. The reverse design of the present dollar debuted in 1935, and the obverse in 1963 when it was first issued as a Federal Reserve Note (previously, one-dollar bills were Silver Certificates). The current US two-dollar bill has the oldest obverse design, dating from 1928.

A dollar bill is composed of 25% linen and 75% cotton. That blend makes the notes more difficult to counterfeit compared to paper (as well as increasing its durability). As of December 31, 2018, the average life of a dollar bill in circulation is 6.6 years before it is replaced due to wear. Approximately 42% of all U.S. currency produced in 2009 were one-dollar bills. As of December 31, 2019, there were 12.7 billion one-dollar bills in circulation worldwide. An engraver at the US Bureau of Engraving and Printing, George Frederick Cumming Smillie, made an etching of a painting of George Washington by Gilbert Stuart which was used on multiple banknotes. A vignette of the portrait appears on the one dollar bill of 1899, and on notes since 1918.

The Shah Mosque (Persian: مسجد شاه, lit. 'Masjed-e Shah'), also officially known as the Imam Mosque or Imam Khomeini Mosque, is a mosque located on the south side of Naqsh-e Jahan Square in Esfahan, in the province of Isfahan, Iran. Its construction began in 1611, during the Safavid Empire under the order of Abbas the Great, and was completed c. 1630.

It is regarded as one of the masterpieces of Persian architecture in the Islamic era. The mosque is registered, along with the Naghsh-e Jahan Square and other surrounding structures, as a UNESCO World Heritage Site. It was added to the Iran National Heritage List on 6 January 1932, administered by the Cultural Heritage, Handicrafts and Tourism Organization of Iran. The mosque is depicted on the reverse of the Iranian 20,000 rials banknote.

The Mercury dime is a ten-cent coin struck by the United States Mint from late 1916 to 1945. Designed by Adolph Weinman and also referred to as the Winged Liberty Head dime, it gained its common name because the obverse depiction of a young Liberty, identifiable by her winged Phrygian cap, was confused with the Roman god Mercury. Weinman is believed to have used Elsie Stevens, the wife of lawyer and poet Wallace Stevens, as a model. The coin's reverse depicts a fasces, symbolizing unity and strength, and an olive branch, signifying peace.

By 1916, the dime, quarter, and half dollar designed by Mint Chief Engraver Charles E. Barber had been struck for 25 years, and could be replaced by the Treasury, of which the Mint is a part, without Congressional authorization. Mint officials were under the misapprehension that the designs had to be changed, and held a competition among three sculptors, in which Barber, who had been in his position for 36 years, also took part. Weinman's designs for the dime and half dollar were selected.

Coin flipping, coin tossing, or heads or tails is using the thumb to make a coin go up while spinning in the air and checking which side is showing when it is down onto a surface, in order to randomly choose between two alternatives. It is a form of sortition which inherently has two possible outcomes.

A tally stick (or simply a tally) was an ancient memory aid used to record and document numbers, quantities, and messages. Tally sticks first appear as animal bones carved with notches during the Upper Palaeolithic; a notable example is the Ishango Bone. Historical reference is made by Pliny the Elder (AD 23–79) about the best wood to use for tallies, and by Marco Polo (1254–1324) who mentions the use of the tally in China. Tallies have been used for numerous purposes such as messaging and scheduling, and especially in financial and legal transactions, to the point of being currency.

The United States Bicentennial coinage is a set of circulating commemorative coins, consisting of a quarter, half dollar and dollar struck by the United States Mint in 1975 and 1976. Regardless of when struck, each coin bears the double date 1776–1976 on the normal obverses for the Washington quarter, Kennedy half dollar and Eisenhower dollar. No coins dated 1975 of any of the three denominations were minted.

Given past abuses in the system, the Mint advocated against the issuance of commemorative coins starting in the 1950s. Beginning in 1971, members of Congress introduced bills to authorize coins to honor the United States Bicentennial, which would occur in 1976. The Mint, through its director, Mary Brooks, initially opposed such proposals, but later supported them, and Congress passed legislation requiring the temporary redesign of the reverse of the quarter, half dollar and dollar.

The Seated Liberty dollar was a dollar coin struck by the United States Mint from 1840 to 1873 and designed by its chief engraver, Christian Gobrecht. It was the last silver coin of that denomination to be struck before passage of the Coinage Act of 1873, which temporarily ended production of the silver dollar for American commerce. The coin's obverse is based on that of the Gobrecht dollar, which had been minted experimentally from 1836 to 1839. However, the soaring eagle used on the reverse of the Gobrecht dollar was not used; instead, the United States Mint (Mint) used a heraldic eagle, based on a design by late Mint Chief Engraver John Reich first utilized on coins in 1807.

Seated Liberty dollars were initially struck only at the Philadelphia Mint; in 1846, production began at the New Orleans facility. In the late 1840s, the price of silver increased relative to gold because of an increase in supply of the latter caused by the California Gold Rush; this led to the hoarding, export, and melting of American silver coins. The Coinage Act of 1853 decreased the weight of all silver coins of five cents or higher, except for the dollar, but also required a supplemental payment from those wishing their bullion struck into dollar coins. As little silver was being presented to the US Mint at the time, production remained low. In the final years of the series, there was more silver produced in the US, and mintages increased.

The Nobel Prize medal is a gold medal given to recipients of the Nobel Prizes of Chemistry, Literature, Peace, Physics and Physiology or Medicine since 1901. The medal for the Nobel Memorial Prize in Economic Sciences, given since 1968, is awarded with the aforementioned prizes.

Each medal has a portrait of Alfred Nobel in left profile on the obverse. The medals for chemistry, literature, physics, and physiology or medicine have an identical portrait of Nobel with different portraits on the peace and economics prize medals. The medals for chemistry, literature, physics, and physiology or medicine were designed by Erik Lindberg. The peace prize medal was designed by Gustav Vigeland, and the economics prize medal by Gunvor Svensson-Lundqvist.