Need Help With Well Wanted Penny (1914 D)

The first red flag, possibly a $2000. coin for $30.00. No one would offer that if it was real for that money.

In case you'd like to research the topic further there's a good reference on NGC here,
https://www.ngccoin.com/resources/c...ed-states/4/

They discuss and show examples of the Most Common Types of 1914 D Counterfeits including:
Outright counterfeit
Added mintmark
Altered date

As noted in previous comments to your post, a helpful diagnostic tip from NGC is to,
"Compare the position and shape of the mintmark to known genuine examples."

As is clear in the images posted in previous comments, and also in reference PCGS coins I looked at (attached), the mintmark position on your specimen appears to be significantly higher than reference coins.

Also helpful was the suggestion to look for weak unusual details. Again, as noted by others, your specimen appears more grainy and pitted than the reference examples.

This is what we call the "close D" fake. Tons of them out there. I bet I've gotten well over a hundred removed from ebay.