Lucia Popp in the movie "Jánošík" 1963 (Rare)
The movie is said to be a sort of "Robin Hood" fugitive story. This excerpt is all I have of it. But it does give us a nice glimpse of the 23 year old Lucia shortly before she made her escape to the West from what was then Czechoslovakia. The language is Slovak.
I'm grateful to Youtube contributor Dobrib for providing some information about it.