inscription on a coin (of arados i think)

[clem.fandango]

Hi everyone,

I think this is a coin of Arados, with a head of Tyche right and a ship's prow on the reverse. Could you help me towards understanding the lettering on this coin, and towards what it means? I guess the lettering is  Phoenician? But I'm not sure what I'm looking for, and can't make much out beyond the series of thee letters which look a little like N's, and do not know their significance... 

13mm, 2.71g, 12 o'clock.

[Pekka K]

That is the date in Aradian era, N = 20. So NNN = 60.
Unfortunately there may be one or two I off flan making
exact date uncertain.

Pekka K

[clem.fandango]

thank you Pekka: can you tell me what the lettering above is / means?