Uncirculated sealed coins can be bought from the mints, and coin collections have verifiable protections and codes. Out in the wild coins have a certain sheen and color to them and once you see good examples of this, with practice you can tell some difference.
I'd suggest the odds are very high at getting that quality in change. It does happen, but finding it like that will drop the rating right away.
But as in everything else collected, counterfeit coins and even entire 'mint' issues have been faked. Ask Zab how that goes with his cards. I've even seen bootlegged and faked 45 rpm vinyl records.
The one thing about China is they are tremendous and proficient counterfeiters.