Here's a decent analysis of the passage.
> It is these seven kings that we want to deal with in this paper. Basically, there are three different interpretations that could be considered about who these seven kings are:
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> **Seven Individual Kings** : This interpretation has a couple variations. Some try to identify seven individual emperors (a typical preterist view), and others seven individual popes.
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> **Seven Kingdoms** : This interpretation typically identifies the first five kings either as being Babylon, Medo-Persia, Greece, Pagan Rome, and Papal Rome; or as being Egypt, Assyria, Babylon, Medo-Persia, and Greece.
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> **Seven Forms of Roman Government** : This interpretation typically identifies the first five kings as being five of the following forms of government: a) kings, b) consuls, c) dictators, d) decemvirate, e) military tribunes with consular power, and f) triumvira