DAM 01-27.1 superior layer is an ʿAbd al-Malik b. Marwān. codex. The palimpsest (the inferior layer of the same MS) is older and is not an Uthmanic codex: the rasm is different, the order of the sura is different, it lacks or add verses, etc., It was effaced to be replaced by the rasm of the superior layer.
DAM 01-27.1 still came from a
complete Quran, which goes against your statement that there was no codex in existence prior to AD 685. The
scriptio superior (maybe the lower?) is dated by Déroche between 650 and 685 CE. The
scriptio inferior is earlier and is non-ʿUthmānic, true, but the differences are, however, exaggerated, and do not change the fact that it is the same book. Actually, the
scriptio inferior confirms parts of the narrative regarding the Companion codices, but that is neither here nor there. Von Bothmer examined the manuscript in question and concluded standard text of the Quran, including the first and the final two chapter, existed in the seventh century. According to von Bothmer, the manuscript includes the ʿUthmānic. What is significant here is that the manuscript includes, as noted before, the two last chapters, typically absent from non-ʿUthmānic codices. Still, this manuscript demonstrated that there was a
complete Quran by the mid-seventh century.
Codex Parisino-petropolitanus was written between AH 50–75. The consonantal skeleton is Uthmanic and is near identical to that of the Cairo edition. But what is of importance here is that this is before the reign of ʿAbd al-Malik (r. 685–705) and the reforms carried out by his governor al-Ḥajjāj b. Yūsuf, who ruled from 75/694 until 95/713. The ʿUthmānic
vulgate and a complete codex, existed prior to ʿAbd al-Malik and al-Ḥajjāj.
Two additional manuscripts are also radiocarbon dated before ʿAbd al-Malik and al-Ḥajjāj with 95 % probability.
However one looks at it, the manuscript evidence does not IMO support a mid-Umayyad codification for the Quran under ʿAbd al-Malik.
Topic: Qur'anic studies today