A manuscript analysis of the Qur'an does present us with unique problems not encountered with the Bible. While we can find multiple manuscripts for the Bible written 700-900 years earlier, at a time when durable paper was not even used, the manuscripts for the Qur'an within the century in which it was purported to have been compiled, the seventh century, simply do not exist. Prior to 750 A.D. (thus for 100 years after Muhammad's death) we have no verifiable Muslim documents which can give us a window into this formative period of Islam (Wansbrough 1978:58-59). In fact the primary sources which we possess are from 150-300 years after the events which they describe, and therefore are quite distant from those events (Nevo 1994:108; Wansbrough 1978:119; Crone 1987:204). For that reason they are, for all practical purposes, secondary sources, as they rely on other material, much of which no longer exists.
We simply do not have any "account from the Islamic' community during the [initial] 150 years or so, between the first Arab conquests [the early 7th century] and the appearance, with the sira-maghazi narratives, of the earliest Islamic literature" [the late 8th century] (Wansbrough 1978:119).
http://debate.org.uk/topics/history/bib-qur/qurmanu.htm
Where then are the original manuscripts? The Qur’anic manuscripts Muslims regard as their earliest; the Topkapi manuscript in Istanbul, Turkey, and the Samarkand manuscript in the Soviet State Library in Tashkent, Uzbekistan, bear the marks of a date of authorship of ~AD 850. They are written in a form of Kufic script which arose in the Abbasid period (~AD 750-850) and are adorned with 9th century embellishments.
The oldest Qur’an, according to forensic dating, is in the British Library. It dates to around AD 790; almost 150 years after Muhammad’s death.
Muslims defend their inability to produce early manuscripts by saying that the Qur’an was originally passed down orally and that early copies have disintegrated. But Muslim tradition itself tells us that the
Qur’an was written down 20 years after Muhammad died and we have other Arab literature that has survived from the 7th century. We know that there were secretaries during the Ummayad Dynasty (AD 660-750) and that Muhammad himself worked on a caravan where written records of transactions would have been kept.
http://www.sullivan-county.com/x/prob_koran.htm