There are two beasts: the first has 10 horns and 7 heads. This must represent Rome and the Julio-Claudian dynasty. Rome famously has 7 hills, but the 10 horns?

The second beast only has two horns, "like a lambs".

Many years ago, (perhaps at teh suggestion of a vicar's sermon?) I had a crackpot theory to do with coins.

In Roman numerals, 666 = 600 + 60 + 6

6 = VI

60 = LX

600 = DC

Now look for a Roman coin of that era with those letters on it. Problem: X appears in Roman numerals of that era but not in any writing.

So, instead let X = V + V.

We are now looking for a widely circulated Roman coin inscribed with the Caesar’s name in a way which includes D, C, L, I, and 3 Vs. (All letters which are not roman numerals are just ignored.)

(Does a Roman “A” qualify as an upside-down “V”?)

Nero coins — ANCIENT ROMAN COIN — OFFICIAL WEBSITE (ancient-roman-coin.com)