This is probably the best single set of stamps ever issued, in my estimation: the 1923 Iraqs. Lovely pictorial designs and lovely colours - the designs based off Babylonian motifs are particularly striking but everything looks pretty great I think. This was the first proper issue of stamps for Iraq - previously they had used Ottoman ones, or overprinted Ottoman ones in the 1917-1923 period. These stamps were also overprinted for government use (bottom picture): in English in 1923, and then English and Arabic in 1924. The issue lasted until 1931 when a new set, all bearing the portrait of King Faisal I, was put out.