Apple II PSU

[David Williams via cctalk]

Anyone have any idea on how to open this particular Apple II PSU? It is 
a Astec AA 11040B and has like a rivet on each side in the middle. All 
the other supplies I've messed with just had screws along the bottom. 
Trying to remove the bottom of the casing so I can work on the supply 
itself. Link to a pic of it.

Thanks for any help.
http://www.trailingedge.com/images/A2PSU.jpg

David Williams
www.trailingedge.com