This imagery of a white stone has been explained in various ways by interpreters: as a badge of acquittal in a legal case, as an expression of welcome by a host to his guest, or as a voting token used by a voter to indicate his choice of a candidate.
Perhaps the most believable explanation is that the apostle John, the author of Revelation, was referring to a white stone given to the winner of an athletic contest. This stone was an admission ticket to the winner’s celebration at a later time. This may refer to the time when faithful, persevering believers will receive eternal life and experience the Lord’s great victory celebration in heaven.
REVELATION 2:17 – To him that overcometh will I [Jesus] give . . . a white stone.