June 17 (Bloomberg) -- Moody’s Investors Service, which already rates Sotheby’s bonds below investment grade, or junk, said it placed its debt on review for a possible downgrade.

The review “reflects Moody’s concern that the duration and depth of the current cyclical downturn in the international auction market may be more severe” than originally expected, Moody’s said in a press release.

Moody’s current rating for Sotheby’s senior unsecured notes is Ba3, the third-highest speculative-grade rating. Standard & Poor’s Rating Services downgraded Sotheby’s debt last month.

Before the announcement, Sotheby’s shares rose 13 cents to $13.56 in New York Stock Exchange trading as of 4:15 p.m. While the shares are up 53 percent this year, they’re down from their closing peak of $57.64, reached on Oct. 10, 2007.

To contact the writer on this story: Philip Boroff in New York at pboroff@bloomberg.net.

Last Updated: June 17, 2009 18:02 EDT