According to this FAQ entry, the last five digits of the player's serial number are a production sequence number.

Assuming the knob who wrote the FAQ is correct (and frankly I'm having my doubts about that guy's reliability), does that mean that my friend Tod's "over-4000" sequence number really means that more than 4000 Mk2/2a players were actually made?

I thought it was only about 3000 players total including Mk1's.

So who's got the highest serial number so far?