Do you think this could be a no S 1990 proof that's been circulated? It just looks so sharp. But no shine. Rachel
Proof coins are only issued in sets from the mint. It's generally rare to find any proof coin in circulation. Someone would have to go through the effort of breaking open the plastic holder and then spend the coins at face value. What are the odds that someone was lucky enough to get one of the very few No S cent sets and just decided that they would break open the set and spend the coins. The probability would be very, very, very small. In addition, modern proof coins have a distinctive appearance. If you get any proof cents in change, you'll know it. (pic from PCGSCoinfacts)
If talking about the possibility of finding PRs in circulation, you're absolutely right. It's not a common thing, but they're certainly out there. In fact, I've personally freed a fairly sizable number of them over the years simply because of the low value. Finding a 90-S no S though, one might have better odds winning the powerball, twice.
And just to confirm it, over the years there have been a number of posts here by people who've found them in the wild. No big dogs though...