Jonathan Greenstein is an antique Judaica authentication expert. As the owner, chief expert and president of J. Greenstein & Company, the only auction house in the United States solely dedicated to appraising and selling antique Judaica, he represents rare pieces of antique Judaica and Jewish art.
Greenstein auctioneered a charity auction in 2002 at the Park East Synagogue in New York City. He organized the pieces and made the catalogue for the auction. Shortly after, he received an auctioneer's license and hosted his own auction. In 2003, he founded J. Greenstein & Company in Brooklyn, New York. The Judaica retail gallery and auction house focuses on religious art from the 1600s to 1938. J. Greenstein & Company auctions include people on the auction floor, the phone, and are available via the Web. In 2010, Greenstein moved the company's headquarters to Cedarhurst, New York. By December 2012, 600 people, including billionaire hedge-fund manager and antiquities collector Michael Steinhardt, received Greenstein's auction catalogs. That year, he hosted Jewish Gilt, a Jewish antiques television show featured on The Jewish Channel. In December 2014, Greenstein sold a Hanukkah menorah for $100,000. The menorah was made in Ukraine during the 18th century. In 2016, J. Greenstein & Company hosted an auction featuring 232 rare objects including rare Judaica items belonging to Harvard law professor Alan Dershowitz. Greenstein acquired Zionist leader Ze'ev Jabotinsky's French refugee ID card, and his company auctioned it off in June 2017. J. Greenstein & Company has also hosted and sold celebrity Judaica including Sammy Davis Jr.'s personal menorah, Rabbi Shlomo Carlebach's piano, a seder plate that belonged to Joan Rivers, and items from victims of the Bernard Madoff scandal. In November 2018, J. Greenstein & Co. held an auction at the Antique Judaica & Jewish Art Gallery in Cedarhurst that included Marilyn Monroe's personal Jewish prayer book from 1956, with notations in the margins likely written by the actress. The prayer book was published in 1922. Greenstein called the Monroe auction "the most significant celebrity Judaica we've ever had." It sold at the auction for $21,000 plus fees. At that auction they also sold Judaica from the collection of Jerry Lewis, with items on view at the gallery dating back as far as a Torah binder made in Italy in the 1690s.
Greenstein is also the founder and CEO of Mercy Home Care and Medical Supplies, a medical equipment and disposables company located in Brooklyn, New York.
