Even a single [penny] is a gift from Hell, minted in human lives.- Kazuo Koike
The penny is, of course, no longer a gift from Hell--at least not in Canada. They have been eliminated. Even so, over the years, they changed from real money (when they were copper), to a reflection of real money (when they were zinc), and since 2000, they had been nothing but tokens, created at will (coated steel).
I remember when I discovered that Canadian pennies were no longer copper. A friend of mine showed me a neat trick with a zinc penny and a blowtorch. You can roast the copper penny as long as you wanted under the blowtorch, and apart from glowing red hot, and temporarily losing its oxidized coating, nothing happened. The zinc penny, by contrast, lasted a few seconds before erupting into brilliant flame, the deformed outer copper sheath collapsing onto nothing. I actually thought it was a plastic token before looking up its content on the internet.
The above quote didn't actually refer to pennies--the exact word was sen, a Japanese copper coin, worth 1/100 of a yen. Nowadays, it doesn't have much value, but in the story from which the quote was taken, it was valuable enough to buy the silence of an accessory to a crime. What happened to its value? Did the copper become worthless? The answer is that too many yen were printed.
My wife's grandmother left us a collection of dirty coins, which she had kept hidden through the years of the Japanese occupation of Singapore. A piastre de commerce of French Indochina, dated 1908. A few Straits Settlements 5c pieces ranging from 1890 to 1935. A gorgeous Straits Settlement dollar from 1908. There was a US quarter and a half-dollar, a Chinese coin from Kiang Nan province, which can be ascribed to 1904 from the chop marks (but which wikipedia tells me was restruck several times in the 1920s). A couple of franc coins from 1899 and 1915. A couple of Thai (then Siam) coins, of uncertain age and value. Silver, all of them, but in total, not much. I assume there were rather more of them when the occupation started.
During the occupation, as occupiers typically do, the Japanese issued their own currency--one which (like the occupiers in America) the denizens of Singapore were forced to accept. The power to make money without limit is its own temptation, and the subsequent inflation combined with the disappearance of capital goods and food was the consequence.
After their defeat, the banana currency became worthless. Unfortunately, the British were a few days late in delivering the new currency intended to replace it, so for several days there was no legal money in Singapore. Only those who managed to keep US dollars, British pounds, or gold or silver hidden through the war years could go to the market and exchange them for a bit of rice. It's during these sorts of times that the value of those gold necklaces Indian women are so partial to really comes to the fore. It's so easy to pinch off a link or two.
Silver coins for Malaya (now Malaysia and Singapore) were minted by the British Mint during the war (dates of 1943 and 1945 are common). However, they weren't delivered until after the end of the war, and I have been given to understand that the first thing the local population did upon their delivery was hoard them. Many of these coins never circulated, and a good number of them in all denominations were left to us as well.
In the Japanese movie "For Those We Love", which depicts the lives of kamikaze pilots near the end of the war in Japan, there is a scene in which the local noodle-shop owner wants to cook noodles with egg for one of the pilots about to head off on his final mission. She has no eggs, so she sends one of her assistants to buy some from a local farmer. "But he doesn't take money any more," she protests, so the elder women has to dig up a family heirloom to trade for eggs.
Destruction of the value of currency has recurred through history, with famous examples in Germany, throughout much of Europe, most African countries (Zimbabwe most famously, but even stalwarts like Ghana have had problems).