Flag of the Netherlands. It was already in use for the Dutch Republic next to the Prince's flag that fearured orange and lighter blue.
Location of the Netherlands (orange) in Europe. It is situated at the deltas of major European rivers such as the Rhine and effectively functions as a trading hub for continental Europe.
History
The Kingdom of the Netherlands is the successor state of Dutch Republic that existed from 1581 until 1795, which history and coinage are covered in its own topic.
French period (1795-1814)
The Dutch Republic became a French client state named the Batavian Republic in 1795. The invading French forces were welcomed by a revolutionary anti-Orangist group named the Patriots. The last Stadtholder, William V, fled to England.
In 1806 Napoleon installed his brother Louis (Dutch: Lodewijk) as King of Holland. Louis was quite popular with the population, especially following his attention to the city of Leiden after an explosion of a boat loaded with gunpowder killed more than 150 people in 1807. Louis also moved the capital from The Hague to Amsterdam, although the seat of government never moved. This situation persists even today.
Napoleon was not too happy with the popularity of his brother Louis, and decided to annex the kingdom to the French Empire in 1810. Allied forces defeated Napoleon in 1813 allowing future King William I, son of the Dutch Republic's last Stadtholder William V, to return to the Netherlands and proclaim himself Souvereign Prince. Two years later he became King of the United Netherlands, which included modern-day Belgium and Luxembourg.
The Netherlands until 1830. Belgium became independent in 1830 and annexed the western half of Luxembourg. The western half of the province of Limburg joined the new state, while the eastern half remained Dutch but also part of the German Confederation until 1867.
Belgian Revolt (1830)
In 1830 the Belgians revolted and declared independence. The motivation for the rebels was mostly founded in the difference in language (French vs Dutch) and faith (catholicism vs protestant), as well as the rather autocratic style of governance of William I. On the other hand, Francophone business elites were actually quite happy with the commercially interested king, as well as some portions of the Flemish population. The Dutch intervened to quell the rebellion but backed off not willing to risk a war with France. In 1839 the Dutch accepted Belgian independence, with Luxembourg becoming an independent and neutral state in personal union with the Netherlands.
King William abdicated in favour of his son in 1840. William II feared the revolutions that swept through Europe in 1848 and hastily accepted a liberal constitution, a year before his death. He was succeeded by his son William III who saw all of his male heirs die in young adulthood. A very late second marriage with Emma of Waldeck-Pyrmont resulted in the birth of Princess Wilhelmina, who became the first queen of the Netherlands at the age of 10 in 1890. Her mother Emma acted as regent until Wilhelmina's coronation in 1898.
At the turn of the century The Netherlands was a conservative country which was extremely divided across religious and ideological lines. The rise of parliamentary democracy in 1917 meant that political parties always had to form coalitions. This is the reason why Dutch policies are traditionally a result of compromise and consensus.
Dutch culture and science underwent a second golden age around the turn of the 20th century. Artists such as Vincent van Gogh and multiple Dutch Nobel Prize recipients are from this era.
World Wars (1914-1945)
Until 1945 The Netherlands had always pursued a neutral foreign policy. During the First World War it was spared from a German invasion as the Western Front raged through neighbouring Belgium. While the British navy blockade caused economic hardship, some Dutch enterprises profited a lot from exports to the warring countries. One example is the Dutch-built Fokker triplane, with which Baron von Richthofen (The Red Baron) won many duels in the sky.
But in 1940, during the Second World War, Germany did indeed invade the Netherlands fearing for a British intervention. The battle lasted only 5 days, after which the country was occupied for almost 5 years. The German occupation was initially mild but as the years passed hostilities increased. Allied forces liberated the southern part of the Netherlands in late 1944, but the remainder had to endure a famine and a very harsh winter before German troops surrendered in May 1945.
After-war years (1945-1989)
It took more than a decade to rebuild Dutch infrastructure, but after that period the economy grew rapidly. The 1970's saw the establishment of a welfare state but also economic challenges as the left-wing government's spending went out of control. Dutch political history resembles that of the UK and Germany, with center-right business focused governments winning most elections in the 1980's bringing business-friendly reforms at the expense of welfare programmes.
Modern history (1990-date)
The 1990's saw a Dutch economic boom which continued up to the Dot Com Bust in 2001, followed by a somewhat strange period of political turmoil and a mild recession. The effects of the Global Financial Crisis (2008) were more severe, but almost 10 years later the Netherlands have regained their position as a very dynamic, international and business-friendly climate.
Currency
The first Dutch Gulden was a gold coin minted in 1378 which was based on the Florentine Fiorino d'Oro. As in Dutch this was translated to Gulden Florijn (Golden Florin) the Gulden was locally abbreviated to f. or fl.
Through many iterations debasements it was standardised in 1693 to contain 9.6 grams of pure silver. Guldens remained in circulation during the Batavian Republic (1795-1806) and the Kingdom of Holland (1806-1810). The latter state was the first to abolish the provincial coinage and introduce a national coinage minted in Utrecht, which is still home to the Dutch Royal Mint today. Therefore, coinage of the Netherlands starts in 1806, and not in 1815 with the establishment of the Kingdom of the Netherlands.
During the French annexation (1810-1813) the French Franc was made the official currency, and the Utrecht mint started minting Francs, although in low quantities. In practice the old Dutch Republic coinage remained frequently used.
The Kingdom of the Netherlands reformed the Gulden in 1816, abolishing the subdivisions of Stuiver and Duit and introducing the Cent. The silver content of the Gulden remained the same at 9.6 grams, but was lowered slightly to 9.45 grams in 1839. The currency was also subject to a gold standard at 0.60561 grams of pure gold. The silver crisis of 1873 forced the authorities to use a gold standard only at 604.8 mg. With this standard, there were 12.10 Guldens in a British Pound and 2.49 Guldens in a US Dollar.
During the interwar years the gold standard was suspended in 1919 but reintroduced in.1925, only to be suspended again during the Great Depression in 1936. Despite the downturn in the Dutch economy the Gulden remained strong, mostly because the government adhered to strict austerity measures in order to limit debt and the risk of devaluation. By 1940 the Gulden had increased in value to 7.6 Gulden per Pound.
During the German occupation the Gulden was pegged to 1.5 Reichsmark, with the Gulden of unoccupied overseas territories pegged to pre-war rate Pounds or US Dollars. Uncontrolled money printing during the war led to a risk of hyperinflation, but this was countered by demonetising all paper money in October 1945.
After the war the newly organised Gulden was pegged to the US Dollar at a rate of 2.65/$ as it entered the Bretton Woods System. In 1949 it was devalued to 3.8/$, but as the Dutch economy recovered in the years that followed, the Gulden was revalued to 3.62/$ in 1961.
After Nixon abolished the Dollar's peg to gold in 1971 the Gulden's value started floating, mostly following the value of the Deutschmark, but nevertheless declining in value from 1.10 to 0.87 DM in 1985. After that the Gulden was tightly managed to follow the Deutschmark and both were replaced by the Euro in 1999, with banknotes and coins following in 2002. The Euro conversion rate was 2.20371 Gulden.
Coins
Kingdom of Holland (1806-1810)
Coins were minted of 10 Stuivers, 1 Gulden and 50 Stuivers. Mintages were low so they never saw widespread use. Gold ducats, nominally worth 5.25 Gulden, were minted for use as trade coinage.
Mint and privy marks
Dutch coinage retained the practice of using privy and mint marks up to this date. Since 1817 the Utrecht mint has been using the mercury staff as a symbol of commerce. For every director the mint there has been a privy mark. A star was added to the privy mark in cases of an interim director.
Willem I (1815-1840)
Before decimalisation in 1816 Silver Ducats were minted worth 2.5 Gulden. They were still in the name of the United Provinces even though the country had become a kingdom.
From 1817 a new decimal coinage was introduced that consisted of copper ½ and 1 Cent, silver 5, 10, 25 Cents and ½, 1 and 3 Gulden and gold 5 and 10 Gulden. To help the public with the decimalisation the ½ and 1 Gulden showed the amount in Cents as well. Older provincial coinage was demonetised in 1822 but due to coin shortages they remained in circulation for quite some time after that.
The Gulden was debased a tiny amount in 1839, and as a result new 1 and 2½ Gulden with slightly reduced size were introduced.
Willem II and III (1840-1890)
Copper ½ and 1 Cents with a W monogram were continued until 1877. Catalogues have split the types of these coins according to ruler but apart from the privy marks they are all the same. They were replaced by smaller size bronze coins in 1877 with a bronze 2½ Cents added in order to replace the tiny silver 5 Cents coins.
The coins for 5, 10 and 25 were reduced in size but silver content was increased from .569 to .640.
Wilhelmina (1890-1948)
While the bronze coinage was continued, silver and gold coins featured the young queen's portrait until she was crowned at the age of 18 in 1898. Her portrait was again changed to depict her in a cloak from 1910, with the designs of the bronze coins restyled as well.
Copper-nickel round 5 Cents coins were introduced in 1907. They were nicknamed 'evening quarter' as with dim light they were easily confused with similar size silver 25 Cents. As a result square sized coins were introduced from 1910, proving much more popular with the population.
After World War 1 silver content of the ½, 1 and 2½ Gulden was lowered from .945 to .720 following the suspension of the gold standard. To distinguish the new coinage, the portrait was again updated in the 1920's. Gold coinage continued with older specifications but started trading at 25% above their nominal value.
In 1948 the final Wilhelmina series was introduced with bronze 1 and 5 Cents and nickel 10 and 25 Cents replacing the pre-war silver coinage.
German occupation (1940-1945)
As Wilhelmina fled to exile in London, the occupation authorities introduced a 'royalless' zinc series of 1, 2½, 5, 10 and 25 Cents. The coins had no privy mark as the mint master did not wish to be associated with war coinage. Instead of using royal emblems the coins featured other Dutch symbols related to trade and navigation.
Juliana (1948-1980)
The 1948 series was continued with the new queen's portrait in 1950. From 1954 silver Guldens and from 1959 silver 2½ Guldens were added to replace the silver certificates that circulated as banknotes after the war. Nickel replaced silver in 1967 and the size of the 2½ Gulden was reduced.
Beatrix (1980-2013)
It took until 1982 before a coin series featuring the new queen was introduced. The modern designs broke with old traditions with geometric patterns that revealed the value. The 1 Cent coin was not continued and demonetised in 1983. Five years later a new 5 Gulden coin replaced the banknote of the same value. The last Gulden coins were minted in 2001.
Dutch Euro coins were minted from 1999 but only released for circulation in 2002. The Beatrix portrait was continued for this series. A couple of years later the 1 and 2 Eurocents stopped circulating.
Willem Alexander (2013-date)
In 2014 a new Dutch Euro series was released with Willem Alexander, the first male souvereign in the Netherlands since 1890.
https://en.numista.com/catalogue/pays-bas-1.html
(Other than the 25 cent Willem III)
My Dutch collector friend got me into that, and I got him into banknotes in return. On our numismatic Discord community, we refer to the big crownsized 2.5 gulden coins as "Rick's dollars" to wind him up. 
