Sheikh `Abd al-`Azîz al-Harbî
In the first century of Islam, the writing of the Qur’ân was done without the use of dots or vowel marks. But by the tenth century AD, it was being written with dotted letters and full vowel indications. If someone sees these markings, he will immediately know that the, manuscript was written in or after the tenth century AD (i.e. after the first century of Islam).
To estimate the time of writing any Qur’anic manuscript, we have to compare it with similar available texts whose dates are known to us. Authors and scribes used to record the date of their writings at the bottom of their texts. If we fail to find the exact date for a particular text, we can make a close comparison between it and similar dated texts.
These methods are known to Muslims in their researches into both Qur’anic or non-Qur’anic texts. Arabic writing had gone through many different historical and regional styles.
No one can add to the Qur’ân or omit anything from it, because its principal way of being preserved is in the hearts of Muslims. It is written in a correct way in an innumerable number of copies. No one, therefore, can find a copy that is more correct than the one preserved in the hearts of the Muslims.
Source: Islam Today