I found this 1958 Lincoln wheat penny it looks to have a faint D where the mint mark could have been.... . would this be considered a error coin.. would it be a Denver or Philly coin at this point
It looks like a random mark or stain. It needs to look exactly like MMS-006 which was used from 1953-62
Can you find and provide a reference that shows an error like the one you suggested? If not, it's likely to not be an error!!! edit: Added the word "not" to the last sentence!