I wrote these descriptions as a freelance writer for Invaluable.com. They are copyright Invaluable 2016-, and are reproduced here with their permission.

US Dollar Coins

The dollar coin has had a turbulent history in the United States. While historically dollar coins have been popular collectibles, they have tended to be equally unpopular during circulation: especially in modern times, where most people prefer to use the dollar bill instead of the currently circulating dollar coin.

There have been many iterations on the dollar coin, ranging from the early Flowing Hair, through the popular Morgan, up to the Presidential. Until 1971, dollar coins always featured Lady Liberty on the obverse, with a heraldic design, usually featuring an eagle, on the reverse. Following this, the dollar coin has shown notable Americans, such as President Eisenhower, Susan B. Anthony, and Sacagawea.

The dollar coin denomination houses several of the world’s rarest coins: the 1794 Flowing Hair dollar and the 1804 Draped Bust dollar. The 1794 Flowing Hair is one of the first coins ever minted by the United States, and holds the record for the current highest auction sale of a coin: just over $10 million, in 2013. The 1804 silver dollar, while holding a much less significant record at $2.3 million, was actually minted in 1834 for a diplomatic mission. Only fifteen of these are known to exist today, and of those fifteen, six were created in the period between 1858-1860 for collectors.

Quick Facts

• An interesting variety of Morgan silver dollars exist with regards to the tail feathers of the bald eagle on the reverse of the 1878 coin. Originally, the eagle featured eight tail feathers. This was changed several weeks into production because all previous coins that featured the bald eagle had shown it with an odd number of feathers.
• The Presidential series, which began production in 2007, proved sufficiently unpopular as a circulating coinage that it was discontinued  for circulation in 2011. The series will continue for collector interest.
• Trade dollars, which were produced from 1873-1878 as business strikes, were never intended for circulation in the United States, although they were legal tender. Instead, they were made as trade coins for the newly opened Asian markets. It is common for trade dollars that circulated in Asia to have chopmarks, which were used to verify the coin by Asian merchants.

US Fractional & Pioneer Gold Coins

Fractional gold coins were privately-issued coins created to fuel the pioneer Old West, which suffered from a lack of sufficient coinage until the San Francisco Mint opened in 1854. Collectors break these coins down into three periods of issue: period one was from 1852-1856, period two includes coins from 1859-1882, and period three are assumed to have been created from 1883 until sometime in the early 1900s. Period three coins are difficult to accurately date because these coins were backdated by their creators to avoid attention.

Period one fractional coins are typically the most sought after by collectors, as they exist at an interesting crossroads in history. Commerce in the Old West economy was essentially crippled as the only functional national mints were back east, and shipments of coins were often targeted by bandits or other hazards. The only assistance that the government could really offer was to allow the federal assay office in San Francisco to create some coins, but this office never produced anything smaller than a $10 eagle. This did nothing to ease the demand for dollars, half dollars, and quarter dollars.

As a result, jewelers in San Francisco eventually began striking small gold coins in fractional values, with designs based off of the official coins of the time, although bearing different inscriptions. These pioneer gold coins were all made with California gold, which lends a unique, bright luster to the coins, as a result of the higher than average silver content in California gold. While there exists little physical documentation confirming the circulation of these coins in the Old West, many of the coins, especially the period one issues, display significant wear.

Quick Facts

• While period one coins tend to be fairly close approximations of national currency, both in design and weight by value, period two issues are significantly less clandestine. Many period twos feature highly deviant designs and less than the stated face value of gold present in the coin.
• Many period two and period three coins were created with the specific intention of being used as jewelry, which was a popular fashion statement in the 1860s and 1870s.
• An 1854 period one quarter-dollar sold for $48,300 at an auction in 2003. The coin features a design known among collectors as a Defiant Eagle, due to the screaming eagle featured on the obverse. The reverse reads “25 Cents,” and depicts a simplistic wreath design reminiscent of national currency at the time.

Byzantine Coins

The Byzantine Empire was originally known as the Eastern Roman Empire, and most of its coinage follows the pattern of its progenitor. Most coin collectors and historians regard 498 CE as the date of the first official Byzantine coinage, as Emperor Anastasius reformed the remains of the original Roman system. Under Anastasius, Byzantine coins were split into gold, called the solidus, and bronze, called the nummus.

Eventually, the nummus developed new denominations, as the tiny nummus coins did not add up to much value on their own. The additional denominations included 5, 10, 20, and 40 nummi. As time passed, the solidus and nummus system was replaced with a new system called the hyperpyron. These coins were frequently minted in a unique cup shape, which some posit allowed bankers to be able to stack them easily for counting. Others suggest that the cup shape of these coins helped their thin, debased nature resist cracking and bending.

The obverse of a Byzantine coin typically features the face of the reigning emperor at the time of minting, although the Byzantine Empire preferred to display the frontal face of the emperor, as opposed to the most common bust profile. This preference echoed through the ages to influence many European coins in the Middle Ages. The reverse of Byzantine coins featured a prominent Christian symbol, as well as the value of the coin displayed in Greek letters.

Quick Facts

• A gold Zoe and Theodora coin from 1042 CE sold at auction for $190,000 in 2014. Zoe and Theodora were the daughters of Emperor Constantine VIII, and reigned as co-empresses for a mere two months.
• Beginning in 695, Byzantine coins were minted with a frontal face of Christ on the obverse, with Emperor Justinian II moving to the reverse. This marks the first time Christian iconography appeared on a coin.
• The Byzantine Empire’s adoption of religious symbols on its coins were the driving factor behind Islamic Caliph Abd al-Malik developing uniform Islam currency featuring legends on both sides, but no types.

Ancient Coins

Coins first arose in the early Iron Age to better store and transport value, as the previously used ingots became bulky and unwieldy for traveling merchants. Many of these early coins were stamped from electrum, a naturally occurring alloy of gold and silver. These electrum coins were eventually displaced by pure silver and pure gold coinage as smelting techniques improved.

The type and worth of a coin was often defined by the powerful city-states of the time. King Croesus of Lydia (present-day Turkey) is credited with creating the gold and silver standard. Later, Athens used their trade power to popularize their particular standard of silver coins. While all of Greece’s city-states used a drachm, roughly translated as a handful, as a measure of value, the actual weight of this handful varied from location to location.

The concept of types and legends, which holds true today, also originated in antiquity. Types are the designs present on a coin: the face of a hero or the shape of a patron animal. The legend is the inscription displayed on the coin, usually a statement of value or a motto. Many ancient Greek coins show many types but few legends — most of the value was discerned by the size and weight of the coin, not an inscription declaring value. This allowed room on the coin for the head of a popular hero or deity on the obverse, as well as a sacred animal or plant on the reverse, sometimes accompanied by a brief legend abbreviating the city-state of origin.

Quick Facts

• The tradition of putting the heads of famous rulers on coins was not started by the Greeks, who thought it displayed hubris, but by the kings of Ptolemaic Egypt.
• In 2014, a silver tetradrachm from Syracuse sold for just over three million U.S. dollars. Coins from Syracuse are widely held to be the finest coins ancient Greece produced, with crisp stamps and attractive designs.
• The Greeks also began the tradition of printing commemorative coins, especially with regards to winning a major battle or sporting event. These coins served primarily as a political message, although they did retain commercial value.