[rescue] Phaser ink

[Curious George]

Hi,

Does anyone know what, if *any*, differences there are
between the ink sticks for the various (incompatible)
Phaser printers?  (the solid ink printers, that is)

I figure the prohibition on using sticks for model X
in model Y must be one or more of:
- they want to sell you more/expensive ink
- the melting point, flow or drying properties of the
  ink is different
- the *colors* are slightl different which would result
  in color distortion in the resulting images

Of course, there are (trivial) mechanisms in place to
prevent you from putting the wrong ink in the machine
(though those are easily circumvented).  But, is there
any downside (as in "printer damage") to using the wrong
inks?

E.g., why is 840 black different from 8200 black?

[as an aside, I think it would be hilarious to meet
the guy who comes up with the various shapes of these
sticks at a dinner party:  "What do you do for a living,
Joe?"  "Oh, I make sure square pegs won't fit in round
holes..."]