Spotted on eBay, a prototype of a 17-inch PowerBook G4 with a special power connector. It’s not the classic round connector used in PowerBooks, but it’s also not MagSafe, a technology that arrived a bit later.
It is indeed a prototype: the PCB is red, and there are DVT markings on some components.
The connector itself closely resembles what Apple used on the Mac mini when it still had an external power supply. The prototype dates back to March 2004, well before the introduction of MagSafe on MacBook Pro models (2006).