Here is the translation provided by the seller Jiri Saldo from the Czech Republic:
REVERSE "Hungry crown gift Soviet federation it is verification political quandary and bankruptcy five-year plan memory at it you government rob. It is challenge to fight,so that opposite weakness authoritarianism put up strength people and offer resistance,how best you can. People the others country,enslavement Soviet federation with integration and add with to you in your match. Free world is with you. All the authority behove people!!
FRONT: "Czechs and Slovaks, know this: The regime is weaker than you think. Power lies with the people, and the people stand opposed. With unity and courage, organize your strength. Down with the Collective. Insist on workers' rights today. Demand concessions -- tomorrow, Freedom!"

Here is what the original note looks like: