1989 was the last year the US Mint hand punched the mint mark into the die. That would account for the different positions of the mint mark. Worn dies often make the lettering and numerals thicker than coins struck by fresher dies. Also, I don't know how many different styles were used that year. Maybe a more knowledgeable member could tell us. EDIT. IMO not a RPM.
It’s caused by a worn die. You can see the striations on the second coin. There was only one mint mark style used that year.
First there's the worn die. A worn die will produce a flatter and wider letter. Then there's circulation wear which.adds to it. In other words, wear.
