A British antiques collector bought an 18th century silver menorah only to find it had been "Judaised" with candleholders added 200 years later.
Jerusalem-based Martin Stern, who has worked as a restitution campaigner, found the candlestick at a Tel Aviv auction firm.
The piece is thought to have cost thousands of dollars. Mr Stern had intended to donate it to the Israel Museum in Jerusalem, but curators declined his offer after discovering the "menorah" was not a real piece of Judaica.
Mr Stern said: "I looked at the hallmarks, they were genuine and the piece was originally made in the 1780s. But the curator took it apart and showed me what was original and what was fake.
"Are there other Judaised items such as this? I want to know who has the brother or sister piece. That one might not have been Judaised."
Last month collectors warned of fake Judaica on the web, offering hundreds of items, including kiddush cups and yads, which were really cheap replicas.