The Lamb Plateless aka Montevideo Hoop (circa 2006) - 1.9MB
The hoop is held in place by 8mm pins (thus eliminating the need for a baseplate).
The Lamb Plateless run hard - 1.1MB
The Lamb Plateless run from an angle - 1.1MB
More information about these hoops can be found on http://www.jclamb.com/