The Wii was a console best known for its unusual “WiiMote” controller, which used an approachable TV remote form-factor and motion-controls to entice families worldwide to play endless amounts of Wii Tennis. Now, an early prototype for this controller has been sold at auction in Japan, reports Polygon.

Although there are superficial similarities, the prototype controller is a very different beast to what was eventually released alongside the Wii. For starters, it’s designed to be plugged into Nintendo’s previous console, the GameCube, which means it has to be hooked up with wires rather than connecting over Bluetooth. The remote plugs into one of the console’s standard controller ports, while the Nunchuck component then plugs into the Ethernet jack, not the proprietary jack found on the Wii. The sensor bar attaches to a free memory card slot.

In case this bizarre wired configuration wasn’t a big enough hint, this WiiMote was likely an internal company prototype that was never meant to be released. The auction’s winner, Smprp, says they’ve been unable to get the prototype working on retail GameCube hardware (translation via Engadget), making this a $660 piece of history rather than a functioning piece of hardware.

We’ve always known than the GameCube and Wii share a lot of DNA. Infamously, one EA developer referred to the internals of the Wii as being like two GameCubes duct-taped together, and the Dolphin Emulator — originally designed to emulate just GameCube games — now happily plays software from both consoles.

Allegedly, multiple versions of this prototype exist, but we might have to wait a while longer for them to leak out of Nintendo’s tight clutches. We’re particularly interested in trying out the “Nintendo Star” controller, a bizarre device that even Miyamoto admits nobody liked.

This isn’t the first time that we’ve had to wait years to catch a glimpse of a prototype device. Back in 2015, a long-rumored Nintendo “Play Station” device was discovered at an estate sale two decades after it was originally produced. Both are fascinating glimpses at the development process of a company that’s notoriously guarded about its internal workings.