Here's a Nintendo 64DD development kit in pristine condition

Remarkable photos of a pristine Nintendo 64DD development kit have been published online, giving a rare look at a piece of hardware few have ever seen.

The 64DD - Nintendo's disc-based expansion unit for the N64 - is uncommon enough on these shores, since it was never officially released outside of Japan.

These photos, posted on Twitter by YouTuber Shane Luis, show the far rarer development kit version of the hardware. These units were sent by Nintendo to a handful of studios so they could be used to make and test games for the add-on.

Included in the box - which seems to have never been previously opened - are a collection of five blank 64DD development discs. These are coloured blue, to differentiate them from the grey discs released at retail. The same colouring is used for the unit's disk slot.

There's also an N64 test cartridge and several adaptors which fit into an N64's cartridge slot, modifying the console for development usage.

One of these allows for two cartridges to be loaded by an N64 at the same time, via a rather Frankenstein-like contraption:

Nintendo launched the N64DD in Japan in December 1999, alongside Mario Artist: Paint Studio and Doshin the Giant. A handful of further games followed, but the system was quietly put to rest less than a year later. Numerous in-development projects were then ported to the GameCube instead.