It's a Hohner D6 Clavinet. Also featured on Led Zep's "Trampled Underfoot". My band does LLWFH without keys - I always play this one on a bass with a bridge pickup (like a J, PJ or T-Bird), using a pick, and play right near the bridge.
I love the sound of a clavinet. Trampled Underfoot is a great track, with clavinet played by JPJ. JPJ also plays some mean clavinet on Scumbag Blues off the Them Crooked Vultures album from a couple of years ago.