Unwired View uncovered the clamshell patent, which was filed in September 2006, and depicts a device around half the size of the current iPhone.
The clamshell iPod design features a transparent "dual-sided trackpad" cover, which is touch sensitive on the top and bottom. The patent says both sides of the cover/trackpad can be controlled at the same time while the angle of the two screens can be an influence too.
While the designs don't depict a keyboard, the patent implies the sensitive controls would be used to create a virtual keyboard. The patent also highlights the technology could be applied to "other handhelds and computers".