Crete, formerly under Ottoman rule, issued their own stamps from 1898 until 1908, after which the island became an official part of Greece. Many of those stamps are nice collectors' items. Eye candy.
The ancient coin is in Scott called a "Cortyna coin". Cortyna is a strange spelling of the ancient place name Gortyn or Gortyna, today an archeological site 45 kms from Heraklion. And reading further in Scott: "The so-called revolutionary stamps of 1905 were issued for sale to collectors and, so far as can be ascertained, were of no postal value whatever." Well, nowadays they certainly have value for us stamp collectors.
Greece #380 (1975) is another classic Stamp Day issue commemorating the nation's proud past. The head between the Doric columns is from a bronze statue made around 340 BC, popularly called "The Youth of Marathon". It was found in 1926 at Marathon Bay.