A palimpsest is a manuscript that has been scraped clean and used again, and it is valuable precisely because the scraping is never complete. Enough of the first text remains in the parchment to be recovered by instruments that can see what the eye cannot.
The upper text of this manuscript is unremarkable: a Quran that agrees closely with the standard consonantal text established under the caliph Uthman. The lower text is the reason the manuscript matters. It is also a Quran, and it is not that Quran. Its surahs come in a different order. Its wording differs at many points, sometimes in ways that change nothing and sometimes in ways that do not. It is the only physical witness anyone has found to a Quranic textual tradition standing outside the Uthmanic one.
Recovering it took decades and several technologies. The cache was found in 1972, the palimpsest identified in 1981, and the lower text read progressively through ultraviolet photography and then X-ray fluorescence imaging, with substantial publication only from the 2000s.
The manuscript therefore bears directly on how the Quran reached its standard form, and it does so as evidence rather than as argument. What it shows is that the standardisation described in the Islamic historical tradition left something behind, and that at least one copy of what was left behind survived because a later scribe needed the parchment.