The Disc - A Mysterious Relic of the Pre-Gardens Era

Wherever the Disc came from, it must have been untouched by human hands for centuries. When artifacts are lost for long enough, fewer and fewer are left to remember that it was ever lost. Eventually, no one can even remember what it's supposed to be.

The Recovery

The Disc was uncovered in a cache located in western Europe. Union investigators hypothesize that the site was a bomb shelter, as it was embedded into the ground and built out of reinforced materials. The composition of the building does not suggest that whoever built it had access to a Creative Engine, as a more suitable material alloy could have been used than lead. It's presumed that a stronger material simply wasn't as readily available in the Pre-Gardens era.
The following is an excerpt from the official report from the investigation:

IUN Archaeological Survey Authority - Report #344. July 2nd, 2820
The structure has only one entrance, a massive door. After spending a great deal of the day attempting to open the door, we presumed that the inside had been sealed away for potentially hundreds of years. Thus, our investigation took great care not to disturb evidence if possible.
Collins, in one of the rooms, uncovered a skeleton. In its bony hands it held a shimmering, round disc. We recovered the object for later examination, but Collins and I just felt uneasy about the whole thing. Whoever that was died holding this thing, so it must have meant a lot to them.
The more I look at it though, the more confused I am. It's a rather unassuming object. The sides of the disk are very reflective, enough that I could use it as a mirror if it weren't for the hole in the center.
There are some scratches on the disc, which is to be expected given its age. However, I'm intrigued by the patterns of the scratches. There are several scratches, but one in particular runs around the disk in a perfect circle. I'm imagining that perhaps the disc was spinning when it occurred, else the scratch might be more wobbly.
Collins suggested that we name it the Shining Donut, but I disagreed. I'm the Senior Surveyor for a reason, you know. 

The Analysis

The Disk was sent back to Las Calles for analysis by some of the Union Archives' few researchers. They were able to scan the Disk and reproduce copies with the Creative Engine for further study while keeping the original safely intact. The copies even retained the scratches of the original. 
There were many different theories as to the function or purpose of the Disc. It was hypothesized to be a decorative object, or perhaps it was part of a larger set as a hanging or arranged array of mirrors. However, the hole in the center and the scratches don't align with either of these theories. 
After examining the copies through more destructive means, it was revealed that the inner parts of the disc were built in layers with alternating shapes of tiny mirrors. Based on the patterns, one of the archivists proposed that it was possible that the Disc may have been some kind of archaic data storage method. This might explain why the scratches appeared in a circular pattern, as the Disc may have had to spin in order to be read by a machine that could see the patterns of reflective mirrors. 
However, the question remains as to why such an inefficient storage method was being used in the pre-Gardens era. Surely by the time the Gardens were created or under development, such Discs wouldn't have been in use any longer. Whoever was able to construct the generators that power the Gardens and the Creative Engines must have had extremely powerful technology far beyond something like this Disc. It's possible that it might have been a relic from much longer ago than the Gardens.