If you wish to pursue a possible claim
To pursue a possible claim for a work of art with Nazi-era provenance, visit The Art Loss Register, the largest private database of claims for missing art works. The ALR will take the details of WWII-related claims and then will search for the objects as part of their ongoing work. You can find them at http://www.artloss.com.
The Holocaust Claims Processing Office of the New York State Banking Department (HCPO) may also be able to help you in your search. The HCPO is an agency of the New York State Government that helps individuals of all nationalities and backgrounds obtain fair and just resolution for the theft of property in Europe during the WWII era. The HCPO charges no fee to pursue claims, nor is its service contingent upon a percentage of claimants’ restitution awards. You can reach them at http://www.claims.state.ny.us, phone 212-709-5583.
Finally, there are a number of websites in Europe which list missing objects taken from European nations or their citizens from the WWII era, or list found objects for which claimants have not been identified. These include: