Ok, here's the rest of the funny story:
I own a small company. And we send out about 70 or 80 customer bills per month. So I can easily go through a roll of 100 stamps per month. At a certain point, in the early 1990s, I discovered this was the perfect way to quickly get rid of coins. Afterall, you can pump them fast into the machine than you can to roll them in paper wrappers! And the post office charges no fee like coin-star. Thus presto, the perfect solution to putting coins back into circulation, eh ? And at a certain point, realized that by hitting the "return" button, at any point, gave me back clean coins (versus the coins I'd just put in). So it became a combination of buying stamps, plus randomly hitting the return button for any overages.
This went on for about a year. 1x p/month, I'd go down late at night (the lobby doors didn't close till 8 or 9pm), and put $50 or more into the machine .
However, one time, as I say, the machine jammed. The counter read somewhere approaching $30. And I didn't want to walk away from my money. I noticed an after-hours buzzer button in the lobby, so I pressed it. Explained the machine wouldn't let me make a choice of stamps, nor get a return, because it was jammed. The postal worker reached for his keys, to open up the machine. All of the sudden, I'm thinking
"oops. I hope he doesn't look at my coins I just put in !"
He looked through various track mechanisms. And then reached for the coin-tray of recently entered coins. There was a moment of silence .......

All of the sudden the guy spun around, stared me deep and hard, and yelled "
YOU !!" 
At first I played dumb , like "what ? What's up?". Then he got specific and said "you've been bringing in all these dirty brown and green coins every month, right ?" I sheepishly admitted it was me (no denying it)
So he explained the following funny story: He is/was actually the employee tasked with servicing that machine, emptying the contents, and rolling the coins to go to the bank for deposit. And every month ...... like clock-work, he would bump into $50-ish of these odd-ball brown and green coins! He would stop, inspect some, and realize they're actual coins (and not slugs or fakes or whatever). So .... not knowing what else to do, he simply rolled them in with all the other post-office deposits that go to the bank. Hey, afterall, they're legal tender, right ?
That went on for about 6 months, no problem. However, one day, the bank called to complain. The call got routed through several channels and layers of the post-office, till finally the complaint landed on this guy's desk (they traced the dirty coins back to this particular employee's work station or whatever). Eventually the post office's stance to the bank was
"that's your problem. They're legit coins. What do you expect us to do with them?"
The reason the bank themselves had complained, was that they , in turn, had been passing coin-rolls on to other consumers/bank patrons. And it was THOSE PATRONS who had come back to the bank to complain. The bank, in turn, traced the deposit # (written on the sides of each role ) back to the post office.
The bank did not have an answer to the post-office. Admitted they apparently could not decline them, because, yet, they were actual coins. So they left the post-office alone, and nothing ever became of it. Yet month after month, this worker kept encountering hundreds of these dis-colored coins, and a mystery "was afoot" at the post office. Everyone wondered where are they coming from?
I was shivering in my boots thinking "I'm in big trouble"

But the other side of me is thinking "I've done nothing wrong, have I ??
The guy asks me "where do you get these ??" I explained my hobby of detecting. And he ended up saying he personally doesn't care. And that the bank, apparently, was forced to accept them. He was just more amazed than anything, to finally un-ravel the mystery. We went on to talk about detecting, and how it works, the different brand/type detectors, etc..... But I'll never forget the moment he spun around, looked at me, and yelled YOU !! :blush: