At Exodus 28:26, where God was describing the High Priest’s official clothes, He told Moses:
‘You are to put the Revelation and the Truth (Greek: ten delosin kai ten aletheian) on the Expression of Judgment, and Aaron will wear it on his chest whenever he enters the Holy Place before Jehovah.’
Notice that the Greek word deloson means revelation and the word aletheian means truth. So, these are the terms used in this translation.
Unfortunately, this description is only found in the Greek Septuagint. Exactly what the Revelation and the Truth is, isn’t identified. However, tradition has it that this item (which the Hebrew Masoretic text refers to as the Urim and Thummim) was used in some way to indicate God’s decisions to the High Priest.