1951 D Lincoln Wheat Cent Mint Mark D Is Touching The 5in The Date

viola133- no not really. The mint marks were individually punched, so their exact placement on the coin beneath the date often varied a bit. IT would only truly be an error if the mint mark were actually over or beneath the date. This issue continued into the past couple of decades. IN fact, I have a 1986 D which has a mint mark that is very low and tilted diagonally, and this is not even really considered an error.