Czechoslovakia Overprint On Hungarian Stamp

i Assume that this stamp is right after the collapse of the austro-hungarian empire. And used by Czechoslovakia until they got their own stamps. Czechoslovakia was formed in 1918 and lasted until 1992.
does any one have any additional information about the stamp.
mayby im wrong in my assumptions.

You are right. That is a Hungarian 1916-18 Scott 109 3f red lilac "Harvesting Wheat" stamp that has a type "b" overprint issued in 1919 for Czechoslovakia (Scott B74 20 cents). This is actually a semi-postal stamp which, along with the other 122 semi-postals (some derived from Austria, some from Hungary), was sold at 1 1/2 times face value at the Prague P.O. Philatelic window to benefit charities according to Scott.

Thanks Jkjblue.
Always nice to learn more.