Pokémon Go (and the NES Classic) may be making a lot of headlines for Nintendo at the moment, but news has just surfaced regarding a piece of hardware from the Japanese firm's history: the 64DD, a disk drive add-on for the N64.

The 64DD launched in Japan way back in 1999, but it never expanded outside of the country during its 14-month lifespan - probably because the peripheral and its ten titles were a total flop. Despite allowing owners to use Nintendo's proprietary 64MB magnetic disks, only 15,000 64DDs out of the 100,000 produced were sold.

While four of the 64DD's games were just different versions of Mario Paint, there had been a number of projects announced for development, including various Pokémon titles and a direct sequel to Super Mario 64.

Despite this failure, it seems that Nintendo had considered launching the add-on in the United States. Former Sierra game developer Jason Lindsey announced on the Assembler Games forums that he had acquired a "prototype for the US version of the 64DD," which he probably got from the Nintendo of North America offices located 20 minutes from his Seattle home.

It's thought that Lindsey's device is almost certainly a retail prototype, rather than a dev kit, as it boots up and displays instructions in English. Speaking to Ars Technica, Nintendo support specialist Mark Deloura said: "You couldn't boot into the DD units hooked up for development. That is a sign of it being a retail unit, or at least 'retail-ish. My recollection is that the development DD wouldn't boot at all."

Interestingly, the 64DD Lindsey acquired had one of the blue disks already inserted, but his device is unable to read it. He's asking people for help to get the disk working so he can find out if it contains a unique game or demo that was never released for the 64DD.