The scenes of what appears to be IMF agent Crystal Walker (Mary Ann Mobley) performing on the trapeze were actually performed by circus performer and occasional actress Sunny Woods, who bore a striking resemblance to Mobley.
The words "Államvédelmi Hivatal" appear above the schematic on the board in the prison guard commander's room. This is Hungarian for "State Protection Office" or "State Security Office". From 1948 to 1956, the "Államvédelmi Hatóság" (State Protection Authority) was Hungary's secret police force, basically an extension of Soviet security, but was reined in starting in 1953 by a reform government until the suppression of the Hungarian Revolution of 1956, after which it was replaced by another office essentially run from Moscow.