http://cgi.ebay.com/1976-Alembic-Series-I-Long-Scale-Bass-Case-DS5-Power_W0QQitemZ7359981387QQcategoryZ4713QQrdZ1QQcmdZViewItem

I was looking at that listing this morning.  It's a nice looking bass.  The top wood, which appears to be Purpleheart, looks nice in the pictures.  The bass apparently does not have a back laminate; and the body may be Maple.  The neck appears to be Maple with Walnut.  My guess is that the description of the electronics in the listing is inaccurate.

From one of the side-ish views I would say the back laminate is there, just a different wood than the front.