Not at all what I expected a gendering machine to be.
Crap. VENDING machines.
We had one in the house growing up. M&M’s.
What I learned in my misspent youth was that a deft touch on the handle/knob (think … monkeying with the knob on a dial safe) … delicately moving the knob first clockwise a tiny bit, and then counter-clockwise a tiny bit, over the course of its full rotation … would give you probably 5X the number of M&M’s that a normal rotation would.
I loved M&M’s.
Still do.
But … basically … no more larceny in my heart 
Yeah, it’s a pretty simple mechanism, if you can get the opening to stay under the reservoir of goodies for long they might just keep coming. Most of the ones I see these days dispenses prizes in a clear plastic container about an inch or so in diameter and I don’t think more than one can make it’s way through the mechanism.
I used to service soda vending machines and I’d find all sorts of junk in the change box that people tried to put through. That was nothing though, a friend was in the coin counting business selling and repairing coin counters and vending mechanisms. He encountered every kind of slug anyone ever tried, plus all sorts of trash jammed in the mechanisms.
From long ago experience as a kid. There are lots of ways to drop the wrong coin into a gumball machine that results in a) no gumball and b) you can’t get your coin back. A grown-up with a simple tool could probably fish a stuck nickel out of a quarter accepter in a couple seconds. Yours truly at age 6? Not so much.
Yeah. In our house, the business end of a butter knife worked a jiffy for removing the wrong coin from the slot.
It wasn’t Lock Picking Lawyer stuff 
I don’t remember ever being able to turn the handle past its ‘parked’ stop without the correct (size) coin.
From memory as a kid who probably tried every type coin in every type gumball machine:
If the coin was too big in diameter it simply wouldn’t fit the slot. If it was too small it fit the slot but the handle wouldn’t turn. Then you had to try to get it back out with your fingernail. If you couldn’t get it out it stayed there till a manager fished it out with a screwdriver/butterknife/paperclip/etc.
I believe some models did let the handle turn keeping the smaller coin but delivering no gumball/prize.
Yes, yes, we got that it’s a vending machine. But a vending machine that sells genders? And for just a quarter? I didn’t know they could even do that back in 1965!
ETA: I always keep a pile of quarters around for use in vending machines (mostly for laundry and those machines that sell palatable water). Sometimes I get a Canadian quarter mixed in. I can’t tell the difference between them and American quarters (other than the picture on them), but vending machines can. They don’t jam. They just fall back out of the return slot.
When Japan came out with the 500 yen coin, it was discovered that the Korean 500 Won (?) coin would worn. IIRC it had a value of one tenth of the Japanese coin.
Some ticket machines would let you insert multiple coins and then give change back with new coins, not returning the ones you inserted. Apparently people were arrested for going overboard.
Then there were the altered magnetic calling cards which were popular in the 90s . . .
What can I say? San Francisco in the Sixties, amirite?
Modern vending machines, or rather the coin acceptors, use other things than just size to tell if it’s got a valid coin. Weight and electrical properties such as resistance are among them. US quarters are made of a metal sandwich while Canadian quarters are nickel-plated steel, so they’ll have different resistances.
I am totally cracking up thinking about @ kaylasdad99 seeing his rather entertaining auto correct mistake from 2016 show back up.
Are vending machines coming back now? The only place I remember seeing with a loose treat dispenser (4 kinds) was covered with duct tape when the place opened up after the shutdowns.
The office building I used to work at had over 80 people using the machines in the break room in that wing, now there are about 30 people in the entire building because the rest are WFH. Many of the public places with vending machines have closed or limited access. I hadn’t even thought about the impact of the pandemic on vending machine owners until now, but I’m guessing its not very good for them.
??? Are you referring to Post #19 above? That was from November 16, 2020 not November 2016.
Not related to wrong coin usage but the vending machine at my work about 10 years ago had a weird glitch where if you put money in the slot, it would reject instantly but still “accept” the coin, so you could basically get anything in the machine for free by just reusing the same quarter.
Everyone had a blast “cleaning out” the machine within 3 hours but everyone should have also expected the company that restocked the machine to notice no profit, threaten to sue my work for theft, and my work to bring down the hammer and demand they get enough money anonymously to pay back the company or else they’d manually look up security camera footage and garnish the wages of everybody who stuffed the machine as well as fire them if they were blatant with it.
Jeez, they really acted like stealing was wrong, huh?