I really this is an honest question - otherwise you would join my little club of special posters for adding to my frustration. I wrote no such thing. I suggest you forget the word "shiny" when discussing coins as the only coins that are shiny are POLISHED. Proofs are not shiny either. What has been said above is that a $20 has original mint luster over the entire coin. Since most of the die wear that puts the grooves in the die that produces the luster happens in the field starting near the rims, the luster on a coin's relief starts out less reflective (as the die wear starts) because the grooves in the relief part of the die are less developed/pronounced. The entire coin reflects light. I just pulled a baggy, beat up, circulated (XF+), dark gray colored 1991-P Jefferson nickel out of my pocket along with a 2022 BU Lincoln cent and an AU Roosevelt dime that I received in change at lunch. Each of thes coins has luster under my 100W light. The luster on each looks different. Coins have luster! The type of luster collectors need to learn is the original Mint luster on the cent. When the cent gets a little wear on Lincoln's head, that part of the coin will still reflect light (the luster of circulated copper) but it will look differently than the reflection (luster) from the field.