Larry s, everytime Ayre does anything to one of their products, the serial number will change to reflect this in their production run. Mine is a 9M... indicating it has the latest upgrades incorporated since "M" is the latest production serial number. If they do something else to the player, it will become 9N.... and so forth. Keith's unit above was a "B" series. They only advertise "Major" upgrades. The nice thing is, you can send your product back for any substantial upgrades and get the others also. Mine came as an "Evolution" unit so it says CX-7e. I sent my V5x for the "E" upgrade.
Some of the upgrades are relatively minor. The Evolution is not minor. Hope this helps.
