Rev. 1:9-11 (ESV)
I, John, your brother and partner in the tribulation and the kingdom and the patient endurance that are in Jesus, was on the island called Patmos on account of the word of God and the testimony of Jesus.  I was in the Spirit on the Lord's day, and I heard behind me a loud voice like a trumpet  saying, "Write what you see in a book and send it to the seven churches, to Ephesus and to Smyrna and to Pergamum and to Thyatira and to Sardis and to Philadelphia and to Laodicea."
Write what you see in a book and send it to the seven churches, to Ephesus and to Smyrna, and to Pergamum, and to Thyatira, and to Sardis, and to Philadelphia and to Laodicea.” Here we have the specific audience for this letter. It does not mean that this letter has nothing to tell us, but it has no more to tell us than it had to tell them. That is any proper understanding of the Book of Revelation will be an interpretation that these seven churches would also have had. This means that locusts are not code for Apache Helicopters etc. It was written for the comfort and admonishment of people who lived in Asia Minor at the turn of the first century just as a persecution was about to come on them.