March 1939. Czechoslovakian stamps were issued with the new hypenated name.
Below that, you have three stamps from Slovakia. The first two are presumably from the autonomous Slovakia, when it was still part of Czecho-Slovakia; curiously, the text states Slovenska Posta - perhaps another feature of autonomy. They are overstamped, though, with "Slovak State". However, the third stamps, with a very similar design, makes no reference to Czecho-Slovakia, so this is presumably from the later "independent" period. Also interesting is the fasces, presumably in this instance from a feeling of affinity with the Italian Fascists.