EDIT: Hooray, I kept my promise!
The Czech Republic, or Czechia (Česká republika) is a landlocked country located in Central Europe, bordering Germany, Poland, Slovakia, and Austria. It is situated in the mountainous valley region historically known as Bohemia (Czechia, or 'Čechy' in Czech) and Moravia. It currently has a population of approximately 10.5 millions as of January 2018.
(left) Flag of the Czech Republic, in use since 1918 (for Czechoslovakia), and since 1993 for the Czech Republic.
(centre) Arms of the Czech Republic, consisting of the Bohemian double-tailed lion, Moravian checkered eagle, and Silesian eagle.
(right) Arms of the Czechoslovak Republic (1918-1939, 1945-1961); also includes Slovak, and Ruthenian emblems
History
The first incarnation of this country would be the Duchy of Bohemia founded in 870 AD, which later would become the Kingdom of Bohemia in 1198. Prague throughout the Middle Ages and Renaissance was an important centre of politics and culture, with the Thirty Years War (1618-48) famously starting due to imperial councillors being thrown out of a window in Prague. From 1627 the region came under more and more direct Habsburg rule, and by 1806, with the Holy Roman Empire's dissolution, it became part of the new Habsburg dominion of the 'Austrian Empire'. It would stay that way through for the next century, or so, until the Austro-Hungarian Empire's implosion following the Central Powers' defeat in WWI (1914-18), saw the Czech and Slovak peoples under the Empire's rule proclaim independence, on the 28th October 1918, and two days later the Slovaks joined the new state.
The nation was formally recognised by the victorious Allied Powers and the new Republic of Austria with the signing of the Treaty of Saint-Germain at the Paris Peace Conference in 1919, and Czech statesman Tomáš Masaryk became the young Czechoslovak Republic's first President, under a new Constitution. Initially the new Republic faced ethnic division in it's territories, but having inherited over two-thirds of the Austro-Hungarian Empire's industry, Czechoslovakia's industrial sectors boomed, ushering in a period of economic prosperity in the 1920s, allowing for progressive social reforms that helped bridge the aforementioned ethnic divides. The nation remained the only democratic state in Central-Eastern Europe from 1934 onward, as financial depression saw the rise of totalitarian regimes in its neighbours.
The First Czechoslovak Republic (1918-38)'s borders (left), and it's 1938-39 partition by Germany, Hungary and Poland (right)
Masaryk was succeeded in 1935 by a disciple, Edvard Beneš, and died in 1937. This was shortly before the greatest travail that the young Republic would face; in the summer of 1938 unrest in the Sudetes (Sudetenland) frontier regions erupted as tensions between Czechs and Sudeten Germans broke out, partly funded by the new NSDAP regime in neighbouring Germany.Hitler demanded the 'return' of these regions and their people to the new Reich, and in an effort to keep peace, British Prime Minister Chamberlain flew to Munich to negotiate the transfer of this region to Germany in exchange for 'peace for our time'. Despite Czechoslovakia's 'Little Entente' alliance with France, Daladier's divided government could do little to honour the pledge to the Czechs, and went along with the Munich Agreement, thus the Czech borderlands signed away by the Great Powers in October 1938 without a fight or consultation with the Czechs.
Shortly after the loss of the Sudetenland (and with it Czechoslovakia's formidable 'Beneš Line' defences, and the vast Skoda iron works), Beneš resigned as President, and was replaced by future German puppet Emil Hácha, whose tenure saw the liberal Czechoslovak democracy slide into authoritarian rule. The disputed Zaloizie and Ruthenia regions were taken by Poland and Hungary respectively as well; and finally, German forces entered Prague on 15th March 1939 to 'restore order', turning the 'rump state' of Czechoslovakia into a German Protectorate, 'Bohemia and Moravia' (Bohmen und Mahren/Čechy a Morava), with a Slovak puppet state also being set up under Josef Tiso. The Czechoslovak intelligentsia and dissidents were first targeted; but from 1942 onwards, racial laws were implemented to target 'undesirable persons', as well as 'Germanize' certain regions and peoples. Resistance was brutally crushed; when SS Officer Reinhard Heydrich was assassinated (Operation Anthropoid) by the Czech Resistance, two whole villages were liquidated in retaliation.
Ruins of Lidice, one of the liquidated villages shortly after it's destruction.
From 1943 onwards, the war turned against the Axis; Allied forces bombed parts of the Protectorate in 1945. By the time Soviet forces took Berlin, Bohemia still lay in the hands of German forces, until the unconditional surrender of the Third Reich on the 8th May 1945. The [Provisional] Government-in-Exile of Czechoslovakia was reinstated from London, headed by Beneš once more. The situation had changed; now ten million Soviet troops were strewn across Central-Eastern Europe, Czechoslovakia being one of the countries now in the Soviet sphere. In 1948, Beneš died; disillusioned of the West by Munich, some embraced the new KSČ (Czechoslovak Communist Party), which after the coup d'état in February 1948, slowly grew in influence and power, via Stalinist advocates such as Klement Gottwald, boosted by Soviet funding, until they had a political monopoly by 1960, when the Czechoslovak Socialist Republic (CSSR) was proclaimed.
Poignant 1968 cartoon juxtaposing Soviet troops' reception in Czechoslovakia in 1945, to their putting down of the Prague Spring that year
Czechoslovakia had a late start in de-Stalinization as a result; hampered by industrial stagnation in the 1960s. It had been a founding member of the Warsaw Pact in 1955; but when the liberal Alexander Dubček came to power in 1968, censorship was lifted in the 'Prague Spring', and a liberalizing programme of freedoms of religion and press implemented, in the spirit of Détente. Despite party conservatives' opposition, Dubček's 'Socialism with a Human Face' proved popular; but concern by Brezhnev and the Kremlin saw the August 1968 invasion of Czechoslovakia by the Warsaw Pact. Consequently reformers in the KSČ were purged, and the Pact issued its 'Brezhnev Doctrine' in response to international protests. 'Normalisation' to pre-1968 status was the policy throughout the 1970s and 1980s; but by the later half of the latter decade, Gorbachev's own liberal policies of 'glasnost and perestroika' had contributed to the uprising of anti-communist demonstrations around the Warsaw Pact nations. In 1989, the 'Civic Forum' movement gained traction after a clash with police, and by the end of the year the KSČ had crumbled, leaving the way open for a democratic coalition government to be formed, the first in over 50 years in Czechoslovakia.
By 1992, the new 'free' Czechoslovakia had a new problem in the form of calls for Slovak autonomy getting in the way of the government's functioning, so on the 1st January 1993, the 'Velvet Divorce' saw the Czech Republic and Slovakia in their current form peacefully founded, and the former Czechoslovak state dissolved. The Czech Republic maintains good relations with Slovakia; the are both members of the Visegrád Four group, and share many cultural and linguistic similarities. The Czech Republic joined NATO in 1999, and later the European Union as well in 2004. As of today, it is a successful, developed country with some very advanced living standards.
Currency
Since it's founding in 1918, the Czechoslovak currency has been the Koruna ('Crown' in Czech), based on the former Austro-Hungarian Krone, whose banknotes circulated widely in the first few years of the new Republic, with counterstamps. The first Czechoslovak coins were issued in 1922-23, in denominations of 2, 5, 10, 20, 50 haléřů (h), and 1 and 5 Korun(a) coins. Later on, in 1930 a silver 10 Korun coin, and in 1933 a 20 Korun coin, were issued; as well as a 25 haléřů coin in 1932-33. These coins would circulate until the collapse of Czechoslovakia in March 1939, after which similar 10, 20, and 50 haléřů and 1 Koruna coins in zinc would be issued for the Protectorate of Bohemia and Moravia in 1940-44.
Examples of the minimalist 'modern' designs on first-generation Czechoslovak coins' reverses.
Most of these coins feature a modernist motif, such as the Charles Bridge in Prague, or a woman harvesting wheat on the reverse; with (usually) the double-tailed Czechoslovak lion on the obverse (or a coat of arms), with the legend 'REPUBLIKA ČESKOSLOVENSKA' around it. For the Protectorate coins, detail can be found here. For Slovak coins, here. The 5 Korun coin in particular has changed metals thrice; Copper-nickel until 1928; Silver to 1932, and Nickel in 1937-38. Most of these first generation Czechoslovak coins are relatively available at low prices, even the silver commemoratives in 1928 and 1937 both depicting Masaryk.
Comparison between the pre-1960 (left) and post-1960 (right) lion and legend on the obverses of Czechoslovak aluminium coinage.
Following the Second World War, the pre-war designs continued to appear on coins; circulating coinage was now limited to 20 and 50 haléřů coins, and 1 and 2 Korun(y) coins, whose dimensions had changed from their pre-war counterparts. A short series of silver commemoratives between 1947 and 1951 in 50 and 100 Korún coins is also relatively available. Another new series of coins was issued in 1953, with the addition of 1, 3, 5, 10 and 25 haléřů coins in aluminium, with a 1 Koruna in Aluminium-bronze, still bearing with the 1923 1 Koruna's design. These coins are also very common. From 1960, Czechoslovak coins start to bear the motto 'ČESKOSLOVENSKA SOCIALISTICKA REPUBLIKA' around a modified coat of arms, now bearing a star above the lion. Many low-denomination haléřů coins in the 1960s and 1970s bear a resemblance to East German pfennigs of the same era.
For the brief period of 1989-1993, the Czechoslovak Federative Republic (CSFR) issued similar dimensioned coins bearing the above acronym and a coat-of-arms; after the Velvet Divorce, Slovakia issued coins in it's own Koruna, at par with the Czech Koruna, seen here. The Czech Koruna is still the circulating currency in the Czech Republic as of January 2018, with circulating coins of 10, 20 and 50 haléřů, and 1, 2, 5, 10, 20 and 50 Korún(a)(y).
https://en.numista.com/catalogue/tchecoslovaquie-1.html
https://en.numista.com/catalogue/boheme_moravie-1.html
https://en.numista.com/catalogue/republique_tcheque-1.html
Did I get the it's/its right this time? 
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