What comes to your mind when someone says that something is authentic? Something 'real?' Something 'genuine?' True? Worthy of trust? What about 'reliable?' Believable? Not counterfeit?
In the New Testament times the Romans were in power. There was so much counterfeiting going on that they started the practice of inspecting things. One thing that they checked carefully were bowls, vases, and jars. Very often these items would look really nice on the outside because they were decorated intricately.
The issue was deeper. If the potter who lacked integrity made a cup and it cracked, he would take wax and fill the crack. He would then paint the item with a very beautiful design to cover the wax up. The inspector checking the items being shipped into the Roman empire held the items up to the sun checking for cracks. If there were none, he would put stamp on the bottom that said 'sinceré.' In Latin, this meant:
'sin' meant without, and 'ceré' meant wax
The stamp guaranteed that the item had been inspected and determined to be what it was supposed to be. In 2 Corinthians 4:6-10 it says we carry the light of the glory of God around in clay vessels. We have the stamp of authenticity (the Holy Spirit) inside us.
Many of us think that because we still lust we can not be used by God. Or because you do not have Scripture memorized.... Or because I used to be a [fill in the blank] there is no way God can use me. Wrong! Don't you think God knew about that when He saved you? If you haved accepted Jesus as your Lord and Saviour then God has sealed you with His Holy Spirit (see Ephesians 1:13 & 4:30).
You are accepted.
You now have a new origin and author.
You have been declared authentic.