The Loopz Developer Cartridge: A Game Boy Prototype from Nintendo's Own Backroom

A working Game Boy prototype: an EPROM board with a hand-written label.

Almost everything in this collection was, at some point, a mass-produced object. A retail Game Boy cartridge was stamped out by the million, identical to every other copy on the shelf. This piece is the opposite. It is a Loopz developer cartridge, a working prototype that never reached a shop, and as far as I know only a small number of them exist. Opening the shell reveals not a sealed factory board but something far more intimate: a hand-built test cartridge from inside the industry, complete with a label written in biro.

First, What Is Loopz?

Loopz is a puzzle game, and a good one. It was designed and programmed by Ian Upton, first appearing on the Atari ST in 1989. The British company Audiogenic held the rights, and in 1990 arranged for Mindscape to publish it on computers and consoles around the world. The Game Boy version, released in 1990, was programmed by Argonaut Software, a studio better known for its later work pushing 3D graphics on Nintendo hardware. As games go it is an obscure but genuinely clever little title, the kind of tile-fitting puzzle the Game Boy was made for.

A Game Boy Prototype, Not a Retail Cartridge

What makes this particular cartridge extraordinary has nothing to do with how the finished game plays. It is what is inside the shell. A normal Game Boy cartridge carries a mask ROM, a chip with the game permanently stamped into it at the factory, unchangeable forever. This cartridge instead carries an EPROM, an erasable, reprogrammable memory chip with a little quartz window on top through which ultraviolet light can wipe it clean so a new build can be written in. EPROMs are how games were tested during development, before a final version was committed to mask ROM for mass production.

The details tell the story. The board is printed as a 256-kilobit EPROM development board, the chip is a socketed ceramic part rather than the cheap plastic of a retail cartridge, and across its window someone has stuck a strip of masking tape and written "LOOPZ 10/30" by hand. That scribble is almost certainly a build identifier, a date or a version, jotted down by whoever burned this particular copy. You are looking at a snapshot of the game as it existed on one specific day inside its development, not the polished object that shipped to shops.

Inside a developer cartridge: a socketed EPROM, not a factory mask ROM.

That is the magic of a developer cartridge. A retail copy is the end of the story; a prototype is the middle of it. It is a physical save-point from a moment when the game was still a work in progress, when someone at a desk needed to load this exact build onto real Game Boy hardware and see whether it ran.

The Provenance: From an Attic to the Collection

The history behind this cartridge is as good as the object itself. According to its provenance, it came from the personal collection of the late Steve McKay, a Nintendo of America distributor. After he passed away, his family discovered a cache of these prototypes in the attic and passed them to a local auction house. A batch of twenty to thirty of them came up for sale, and this Loopz cartridge was among the ones I was able to secure, while a number of the higher-profile titles from the same hoard were graded and routed to a major auction house instead.

Better still, these cartridges are not mysteries. They were verified, tested and dumped by the game historian Frank Cifaldi at the Portland Retro Gaming Expo a few years ago, which means their contents have been preserved and their authenticity confirmed by one of the most respected figures in video game preservation. For a collector, that chain of custody, from a Nintendo distributor's attic to a public verification event to this shelf, is exactly the kind of documented history that turns an odd green board into a genuine artefact.

Why Prototypes Matter

It would be easy to see a scuffed prototype as less desirable than a pristine boxed copy, but for a museum it is often the reverse. Retail cartridges survive in their millions; development hardware was never meant to leave the building, was frequently wiped and reused, and was usually thrown away once a game shipped. Each surviving prototype is effectively unique, a one-off that records something the finished product cannot: the fingerprints of the people who made it and the process they used.

This is also why preservation work like the dumping done at that expo matters so much. Every prototype that gets read and archived is a small piece of gaming history rescued before the chip degrades or the cartridge is lost. Holding the physical board is a thrill, but knowing its data is safely preserved is what makes it meaningful. This is not just a rare object; it is a primary source.

A Prototype in the Collection

A hand-labelled EPROM cartridge from a Nintendo of America collection is exactly the sort of piece that pushes this collection beyond the shelves of retail boxes and into the actual machinery of how Game Boy games were made. It sits proudly among the more finished, familiar cartridges as a reminder that every one of them started life as something like this. You can explore the rest of the collection, retail and unusual alike, across the collection.