Although it has nothing to do with Vending Machines, Transportation, or Pay Phones, I recall reading here that the 3-cent coin was introduced mainly because of the price of postage stamps. Large cents were cumbersome and also hard to come by in rural areas.
The East German 20 pfennig was created partly for use in payphones. The smaller aluminum denominations would sometimes jam in the phones, so the 20 pfennig was made in brass to avoid that problem.
Soviet 15 kopek pieces were also used in pay phones. When I was studying in Moscow in 1993, when the ruble was trading at over 1000 per dollar, these coins were still being used in the phones. Since they were otherwise worthless in circulation, they were sold in street kiosks for 15 rubles each.
I also remember reading back in the 80’s that Mexican 1 peso coins were deliberately made to be the same size and weight as a US quarter so that they could be used, fraudulently, in our vending machines. Keep in mind that a peso was one US cent or even less, so it wasn’t like trying to pass the occasional Canadian quarter.
These are some good examples, everyone. So far, I have: DDR: 20 Pfennig. New Zealand: Redesigned $2 coin USA: Eisenhower dollar Any others?
When the US MINT looks at different compositions for coins they include the vending machine "groups". As the method to confirm a coin may include electronic or weight and thus they test/have input on various potential coin alloy changes. You can read about this in the various US MINT Coin Composition documents.
The United States started minting the clad copper coins in 1965 specifically for vending machines. The copper matched the electronic conductivity of the silver previously used in coins.
The vending machine industry KILLED a denomination, the copper-nickel three cent piece. When pay phones came out in the 1880's, they took a dime, which was a lot of money in those days. The three cent piece was the same size, and close enough in weight to pass as a dime in the primitive coin rejection mechanisms of the day. The pay phone operators screamed, and demanded that the U.S. Treasury give them one dime for every three cent piece they had been stuck with. The Treasury told them where to go, but eventually stopped making them and stopped re-issuing any that came in to the Sub-Treasuries.
When the small dollar concept that was eventually issued as the Anthony dollar was being developed in the 1970's, Treasury wanted it to be popular in vending machines, so it deliberately chose a size and weight that did not match any other coin in the world to discourage slugging. That, as you can see, placed it close in size to the quarter. To make it more distinctive, Treasury planned to give it eleven flat sides, which is why the design has an eleven-sided rim. The vending machine industry screamed, and Treasury gave in and made the coin round with a reeded edge. As a result many people could not tell them apart. The confusion was made much worse by the similarity of the designs. Look at the placement of the head, date, LIBERTY, IN GOD WE TRUST, and UNITED STATES OF AMERICA. A bold new design might have worked. As they were, when they came out I spent one as a quarter, and that day I knew that the coin was doomed. When Canada came out with the Loonie a few years later, it learned from the Anthony fiasco and gave the Loonie the eleven sides the Susie was supposed to have. They work fine in Canadian vending machines.
Back in the 80s when I worked in Ireland I found their 5P coin, worth about 7 cents US at the time, would be accepted in US vending machines as a quarter. I would bring back bags of those coins.
There was a great deal of congressional work on the transition to clad coinage. The vending industry had a great deal of pull in the decisions as did the some metal fabricators like Olin Brass. The final composition of 75% cu and 25% nickel alloy explosively bonded on pure copper was effectively "counterfeiting" silver coins already in circulation since vending machines could not tell the debased coinage from the silver. Ironically in the intervening years coin discriminators have become so sensitive that they always will reject silver coinage. In 1999 quarter weight was reduced by 1% apparently so the worn quarters in circulation would continue to work in vending machines alongside the new thicker quarters. Only very recently has the FED begun removing old thin quarters, again for the vending industry though some of these might have been problematical in counting machines. Still a roll of old pre-1976 quarters will be a great deal shorter than a roll of brand new coins. Much of this wear that makes the roll so short is on the rims whose purpose is to protect the design and make the coins countable by stacking.
Half dollars did circulate up until the Kennedy half killed the denomination due to hoarding. In my old neighborhood there was a "steak and egger" diner built in the early 1960's. It had a jukebox (no doubt owned by the Detroit Mafia) and in every booth there was a remote control box mounted on the wall you could play songs from. Little flip pages with the songs and their numbers. Three coin slots. One song was a dime, 3 for a quarter, and 7 for a half dollar. Somewhere in the early 60's our washing machine died and my parents could not afford to replace it, so Ma went to the local laundromat. I went along to help carry. Wash cycle was one quarter. Dryer was one dime. A change machine gave four quarters for a paper dollar. A different machine gave two dimes and a nickel for a quarter, or five dimes for a half dollar. Being a budding numismatist I got all her change so I could check it first, and I remember dropping halves into that machine for her because five dimes were more useful in a laundromat than four dimes and two nickels.
When I was a kid (mid '60's) I remember going into a small roadside restaurant near Paducah, KY with my folks and seeing a juke box that took half dollars. It actually had a picture of a Franklin half near the coin slot. Every Wal Mart I go into these days has self check out which take halves. That's where I spend my CRH rejects.
When I started working in Chicago the CTA issued a small copper-nickel token that worked in both the bus fare boxes and the subway turnstiles. There was also a larger handicapped token that I used, but to use one you had to show the bus driver or the subway booth collector your pass with your picture on it. The small token was the same size as a German one pfennig piece, which was worth about one fourth of a cent. The coin shop I worked in downtown bought in foreign coins that people brought back from trips at a steep discount. The First National Bank of Chicago in the next block had a foreign exchange teller that bought the paper, but they did not want to bother with the coins and then sent people over to us. We kept getting people coming into the coin shop wanting to buy one pfennig pieces in bulk, and they always had some b.s. excuse for why they wanted them. A kid's "art project" was a popular lie. I liked to mess with their heads. One guy said he needed 100 one pfennigs for his kid to give out in his German language class at school. I said "Come on in and I'll take care of you." He came in and I showed him a tray with one hundred somewhat larger but perfect for a giveaway TWO pfennig coins on it, total price to him one dollar. He hemmed and hawed and said that he needed ONE pfennigs. I looked him in the eye and said "Oh no, we don't sell those. Crooks use them in the turnstiles!" He left.
I remember reading something about Frank Sinatra carrying a roll of dimes with him at all times after his son was kidnapped. He supposedly did this till the day he died for good luck I guess. The reason was the kidnappers had him go from pay phone to pay phone with the ransom to assure the police weren't with him and he never wanted to be without a stack of dimes. Maybe an urban myth, don't know for sure.
Not quite the same category, but the British silver 4- penny piece issued in 1837 and 1838 was minted for a very special reason. The standard cab fare for anywhere in Central London was four pence, but Members of Parliament were exasperated by cabbies who, when offered a tanner (i.e. a sixpenny bit) in payment, would claim that they had no change. MPs were forced to leave the extra tuppence as a tip. The problem was solved when the MP Joseph Hume proposed a bill authorizing the issue of a 4d coin, which became known as a "Joey". The new coin however was not popular in the rest of the country as it was easily mistaken for the existing silver three penny bit and was withdrawn from circulation. Joeys have the legend FOUR PENCE on the reverse and should not be confused with silver 4d coins in the name of William IV and Victoria which have a large number 4 in the centre of the coin. These are Maunday coins which were not necessarily intended for circulation
Somewhere around the year 2000 the CTA switched to readable passes and stopped taking tokens, though for a while the busses continued to take exact change in coins. We found out that their central counting room was going to be selling off its accumulation of rejects, and on a lark we bought a ton of it cheap which they delivered in 50 pound bags. I used to go through it during slow times, pulling out coins that were still good exchange and making up poundage lots we could sell. Nothing really good but we probably made money on the lot. Found two or three small Mexican gold coins (the 2-1/2 pesos was about the same size as the small token) and a 1694 Polish silver coin about the size of a nickel. About half of the lot by weight was those German one pfennig pieces. We bagged them up and for all I know they are still sitting in the safe where I used to work!