According to Muslims, the Quran has never been altered by humans down the centuries and is today what it was when first narrated to the Islamic prophet Muhammad.
For this to be true requires a master Quran that all others are copied from, otherwise copying copies leads to errors which become magnified, depending upon the number of copies of copies made. so my questions are:
Where are the master copies of the Quran kept?
How are they prevented from deteriorating over the years?
When were they created?