comment: >
  
  That's the whole point of provenance.  In this case, the seller hasn't disclosed how they came to own the items, but that's being investigated now.  
  Seems to me, the seller really ought to have predicted the shitstorm, and could have avoided any doubts by proving provenance prior to the auction.
context: A sword thought to have belonged to Polish king Sigismund III Vasa has been put up for sale in Germany.
  Posting photos of the weapon on its website, Berlin auction house Carsten Zeige said that the sword “probably belonged to Sigismund III Vasa and came from a pre-war Polish collection.”
  
  ...
  
  Although the seller did not inform how the sword came into its possession, the asking price is EUR 30,000.
  In addition, the auction house catalogue also lists the Order of the White Eagle, Poland’s highest honour, for sale as well as a rapier with a scabbard that belonged to Aleksander Józef Sułkowski, a minister and general during the reign of King August III Sas.
  The auction planned for January 14 has now sparked online fury with many suggesting the items were stolen from Poland during WWII. 
  A report published by the government in London in 1945 about works of art stolen in Poland during World War II said that the Germans and the Soviets plundered about 30 billion dollars worth of unique cultural goods. >
  
  It’s possibly the case, but in theory it could have been in the possession of a private collector of Polish origins and sold without auction or publicly prior to this auction. Alternatively the owner could be someone from Poland and is just auctioning it off in Germany for some random reason. Until you see the present owner and paper work of authenticity and sale history a lot of unanswered questions including that it might be a forgery or just old sword that has been claimed to be the former King’s.