There are so many variations and errors, I wanted to do a little research before I just replied.
I added a comparison image. I put your 1968 S Lincoln Penny reverse, next to a Regular Strike 1968 S Lincoln Penny so we can visually compare the two. The wide am was from all the resources I can see regular or default strike, the standard issue coin.
The close AM versions happened due to die swap errors at the mint, and depending on who you speak with they may say this is just a variety of the coin.
All that being said, it looks like what you have is a later issue strike, one where the die has been worn down and the sharpness of the coin therefore deteriorated by default.
As always though we suggest taking it to a someone in person for a final assessment. We were unable to find any official Wider AM specimens to confirm your assumption, but for we are not the final say so when it comes to the matter. We just provide assistance for coin enthusiast.
Hope this helps.
Thanks for posting Alberto! Please come back and post more when you have questions or just want to talk coins!