The pic you posted is more than adequate to determine what you have. As @paddyman98 said, your coin took a hit that pushed up some metal and left a gouge. You can also see rim damage near the 8. It is not an error.
In 1958 the Mint Mark was manually hand punched into the Die used to strike a Cent. That is why there are examples of Mint Marks that are in different locations under the date. If this "S" looking thing was an actual Mint Mark that person must of been drunk when they created it Once again.. it is simply damage
Not to mention that the "S" Mint wasn't being used in 1958. San Francisco stopped producing coins in 1955. Sometimes, looking at coins is kinda like looking at clouds. Look long enough and hard enough and you're bound to see a fish, a squirrel, or a sail boat.
That is true going through hundreds the eyes start playing tricks.Back in 1958 I think you could drink on the job. I know I would if I had to punch tiny letters on thousands of cents a day. I give those employees credit.Thanks again for sharing your knowledge. McCann
They didn't punch tiny letters on the coin itself... Only onto the Hammer Die with the Obverse incused image that was going to strike the coin. 1 Die with a punched mint mark in the correct location could of struck thousands of coins it was intended for.
