http://cgi.ebay.com/ALEMBIC-EPIC-BASS-5-String-Guitar_W0QQitemZ7403837154QQcategoryZ4713QQssPageNameZWD1VQQrdZ1QQcmdZViewItem

With an upgrade.  Filter/Q?

I don't know anything about the bass.  I'm just passing on the listing as a courtesy.
 
The listing says the controls are volume, pan, bass and treble.  But I see what you mean, one of them looks like a switch.  Or maybe it is a pot with a missing knob?  I don't know, you would have to ask the seller.  
 
Curt

It looks like it has Essence electronics and Q-switch. This would be an upgrade from the standard electronics.  
 
Keith