The crucifix, made of copper and enamel, was crafted in Limoges, France, and was part of a Polish art collection brought to Austria during Nazi rule, Josef Holzberger, police spokesman in Salzburg, said on Thursday.
It was found in 2004 in the lakeside winter resort of Zell am See by a woman combing through a skip filled with the discarded possessions of a neighbor who had just died.
"The lady had a soft spot for old crockery and was rummaging for plates when she found the crucifix," said Holzberger. "She asked the deceased's family, and they said she could have it."
Last month the woman showed the crucifix to a friend who realized it might be something special and took it to a museum.
In the run-up to World War Two, the owners of the crucifix had hid it and other treasures by walling them inside the basement of a house in Warsaw.
They were discovered by the Nazis in 1941, brought to the Polish National Museum and later transferred to a castle in the Austrian village of Bruck an der Grossglocknerstrasse, near Zell am See, police said.
"We lost track of what happened then -- we don't know how the crucifix ended up in Zell am See," Holzberger said.
The crucifix might be worth up to 400,000 euros ($539,000) at auction. Poland's culture ministry has contacted the London-based Commission for Looted Art in Europe, which represents the heirs of former art collectors, Holzberger said.