If you are referring to what looks like a 1 at the end of the date, it could not have come from the Mint like that. Just a well placed hit that looks like a numeral. IMHO.
This pic doesn't do it much justice. But looking at it up close with a jewelers loop it looks like a four.
Your coin has seen a lot of use. Heavily circulated coins have a much higher chance of being damaged. If you closely, the angle on the mark is not the same angle as the 4 in the date, nor is there a serif on the mark. In addition, it doesn't match the 1 on the date. It seems very unlikely that a stray numeral, that doesn't match with the existing date punch would end up on a die. To paraphrase William of Occam, the simplest explanation is usually the correct explanation.
