When a Player Exclusive shoe is made, there's usually a size 9 Sample ran to see how certain production details look. Color blocking, material choice, even letter/number size can be tested and tweaked after seeing a tangible Sample. This is ultimately done to make sure the final products meet the exact specifications needed before the small production runs are sent to the players.
Three-point shooting legend Reggie Miller had a lot of Nike Basketball (and Jordan Brand) SMUs made for him, and the Air Money was one of the pairs that he laced up during his tenure with the Pacers. The Air Money was known for it's unique lacing system that synched up along the side panels instead of over the traditional U-Throat area. I wouldn't say that it was a very popular model, but the overall design was intriguing to say the least.
This pair shown here was an original size 9 Sample from 1996. These were made before producing Reggie Miller's actual Air Money PE, and I believe that the number 31 was slightly altered if I'm not mistaken.