Here's my guess, as I sit in front of a 17" iMac G5....
There's agap between the plastic and the LCD. It shows the clear plastic they use for the case, combined with the white plastic that gives it it's color.
Then I look at my iPod Photo, who's creators also gave us the iMac.
There's no gap over the screen, it's flush. I'm thinking rev B. iMac G5 takes the optical-less edu model, and puts a plastic cover of sorts over the screen.
There's two models: a 1.8 ghz G5 17" with no optical for $799edu ONLY and a 17" 2.0 ghz G5 17", no optical for $999 edu ONLY. Figure that 1.8 ghz G5's for edu is perfect, and given that the no optical on currently costs $999, they could easily drop that $200 and give a similarly spec'd one with a slight faster processor for $999.
Come in with the low end at $699, 1.6 ghz (is it possible?) with 17" screen and 40gb HD (all others have 80gb std, in my model) with no optical and sell it for $599.
So you have protected screen iMacs for EDU at:
$599 1.6 G5 17" with 40 gb HD no optical
$799 1.8 G5 17" with 80 gb HD no optical
$999 2.0 G5 17" with 80 gb HD no optical
This leads the way for new iMacs at:
$999 1.8 G5 17" with 80gb, 512ram, Combo drive
$1299 2.0 G5 17" with 160gb, 512ram, Superdrive
$1499 1.8 G5 20" with 80gb, 512 ram, Combo drive
$1699 2.0 G5 20" with 160gb, 512 ram, Superdrive
I dunno. Pie in the sky maybe, but talk about bang for the buck!