According to the experts, the first Proof U.S. coins were the 1817 large cents. Here is a photo of a Proof 1817 large cent from the PCGS "Coin Facts" site. And here is a high grade business stike example of the 1817 large cent. This piece is graded PCGS MS-66, Brown. I don't know about you, but from the photos, it's hard to tell the difference. I am sure that the Proof surfaces on the specimen coin would be more striking in person.
There are plenty of areas where the differences are discernible, but I agree with you . . . They are not glaring. If the proof had never been messed up, it might possess a noticeably more attractive look than it does.
Seems there may have been some quality control issues with that year. Look at this one extensive die break https://www.ebay.com/itm/1817-N-12-R-3-PCGS-MS-62-BN-CAC-Matron-or-Coronet-Head-Large-Cent-Coin-1c/264279534693?hash=item3d8849ac65:g:rfkAAOSwZVNcr8ok
