500 at the Beginning 500 at the End. Who am I ?

Who am I ?
500 at the beginning, 500 at the end,
5 in the middle is seen,
The first of all letters, the first of all figures,
Take up their stations between,
String them all together, and you will,
The name of an ancient monarch.

Please explain answer.

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Answer is DAVID
500 = D (in Roman)
5 = V in the middle
A = First of all Letters
1 = First of all Figures(resembles I in roman)