The thieves walked into Strängnäs cathedral and stole the jewels last July 31st.
Sotheby's says the auctioning of the jewels is the 'sale of the 21st century'.
None of the stolen artefacts had yet been found, the Swedish Prosecution Authority said in a statement on Thursday. The suspect in the case was not identified by prosecutors.
The thieves, who have not been identified, and the jewels are being sought internationally via Interpol.