There is no such language as "Bohemian" although the word "Boehmisch" was sometimes used colloquially by German speakers for Czech speakers from Bohemia, or German speakers with strong local accents. People in Bohemia, part of the Austro-Hungarian Empire until 1919, now in the Czech Republic, would have spoken either German or Czech. Perhaps the best idea would be to scan the notice into a message and then whichever language it is, it is likely someone could read it for you.