Prototype Apple IIc - Help!

["PMond" <pMond@allinterviews.com>]

Over the weekend, I purchased an Apple IIc at a garage sale in Cupertino. I
have recently purchased several 8-bit machines but this is my first ever
Apple II. I just looked at the bottom and noticed an Apple sticker which
says this is a prototype! The green sticker has the following written on it:
  Apple Computer
  PCSD MFG
  3087 North First Street
  San Jose CA 95134

  Serial Number: P 1529
  Warning: Proprietary Product

As I am not familiar with the IIc line (all my parents could afford were
Vic20s and C64s), I checked some of the pictures at eBay. The biggest
difference I can see between mine and those is that there is an Apple logo
in the top left, but no other writing on the case and the lights and buttons
are not labelled (the keyboard is normal, however) and the ports give no
indication of what they are used for.
So, does anyone know anything about these prototypes and, before I waste my
time listing it on eBay, do you think it is worth something?
Thanks for your time and any information you can provide!
Apple II forever!