What Coin(S) Do You Most Regret Putting Back In Circulation?

The Swedish 10 krona coin is almost identical to the Aussie $2, even remember I got one in change once. I'm pretty sure it has less buying power than $2 but not much. I surely didn't spend it here though.

Was this recently or back when silver still circulated?

If those dimes were rejected someone had to of found them and went walking off with them, if not then they went to the bank and got sent to be destroyed.

I took about a decades hiatus off. My uncle who is a mechanic was saving all the old pennies he has gotten out of the vehicles. Sure as anything a couple months before I really got back into collecting I went to the TD bank and dumped them without even looking in it. Boy do I cringe to this day and this was a little over a year ago only. Got back collecting last June and I check every piece of change I get now. Keep 81 before coppers,all the wheats I find I keep as well. Heck I even have my truck loupe to look at change that I get from stores haha. People look at me like I am crazy when I whip out my loupe in a 7/11 and start zooming haha.

I've never spent a coin on accident, though I have a relevant story.

Once while working at a gas station, my manager asked me to come into his office right after the money truck had arrived with bands of $5's and $1's. He and I had always both competed for silver coins in the registers, but that day he wanted to share. In his hand was $200 in sequential serial # $5 star notes from 2013! In my register, I had laid claim on a $100 star note that came in the cash drawer not too long ago, and had only $100 to spare. I decided I wanted the $5 notes over my $100 star note, so I traded back in the star note to the register, took my remaining $200 to bring home crisp star notes!

Not too long after, I ended up spending all of the star notes to a young couple who were selling silver U.S. coins on craigslist!

I'm positive that I accidentally dropped a 1906 Liberty nickel into my bank's coin machine last year, coming home and realizing the nickel I had found 2 days before was nowhere to be found taught me a good lesson on always keeping my keepers on a different surface than my pocket change.