The “Golden Horseshoe”—sometimes called “Diamond Horseshoe”—was the ring of seats for the rich patrons of the Metropolitan Opera House, at Broadway and 39th Street. The opera house was built in the 1880s and was destroyed in 1966, when the Metropolitan re-opened in Lincoln Center.
 
Billy Rose operated a nightclub called the “Diamond Horseshoe” in 1938 in the Paramount Hotel on West 47th Street.
 
The Auditorium in Chicago also called a row of seats a “Diamond Horseshoe.”
 
     
Wikipedia: Metropolitan Opera House (39th Street)
The Metropolitan Opera House was an opera house located at 1411 Broadway in Manhattan, New York City. Opened in 1883 and demolished in 1967, it was the first home of the Metropolitan Opera Company.
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In 1903, architects Carrère and Hastings extensively redesigned the interior of the opera house. The familiar golden auditorium with its sunburst chandelier, and curved proscenium inscribed with the names of six composers (Gluck, Mozart, Beethoven, Wagner, Gounod and Verdi), dates from this time. The first of the Met’s signature gold damask stage curtains was installed in 1906, completing the look that the old Metropolitan Opera House maintained until its closing.
 
In 1940, ownership of the opera house shifted from the wealthy families who occupied the theater’s boxes to the non-profit Metropolitan Opera Association. At this time the last major change to the auditorium’s interior was completed. The second tier of privately held boxes (the “grand tier”) was converted into standard row seating. This enlarged the seating capacity and left only the first tier of boxes from the “golden horseshoe” of the opera house’s origins as a showplace for New York society.
 
Wikipedia: Billy Rose
Billy Rose (September 6, 1899 – February 10, 1966) was an American theatrical showman.
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In 1938, he opened “Billy Rose’s Diamond Horseshoe” nightclub in New York City in the basement of the Paramount Hotel off Times Square. It initially opened with a version of his Fort Worth show.
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The Diamond Horseshoe operated under that name until 1951.
 
IMDb
Plot Summary for
Metropolitan (1935)
Opera prima donna leaves the Metropolitan to form her own company with Tibbett as leading man. She leaves this company too which means Tibbett and company must carry on without her.
(“Diamond Horseshoe” is another title of this movie—ed.)
   
IMDb
Plot Summary for
Diamond Horseshoe (1945)
Joe Davis Sr., headliner at a big nightclub, is visited by medical student son Joe Jr., who to Dad’s chagrin wants to be a crooner, and soon comes between Dad and his girlfriend Claire. So glamorous dancer Bonnie is enlisted to distract Junior. Which does Bonnie want more, the fur coat or true love? Plot is a framework for numerous Ziegfeld style stage productions.
Summary written by Rod Crawford {puffinus@u.washington.edu}
 
Medical student Joe Davis, Jr., tells his father that he wants to quit school and get into show business. Joe Sr. disapproves, but gives his son a job as a stage manager at his nightclub, the Diamond Horseshoe. Joe Jr. soon becomes smitten with headliner Bonnie Collins, but she has no interest in him. Meanwhile, Claire, who’s in love with Joe Sr., promises Bonnie a mink coat if she’ll go out with Joe Jr. so that Joe Sr. will pay more attention to Claire than his son. Things get more complicated when Bonnie falls in love with Joe Jr. and they get married, much to his Dad’s disapproval.
Summary written by Daniel Bubbeo {dbubbeo@cmp.com}
   
23 November 1884, Chicago (IL) Daily Tribune, pg. 13:
NEW YORK, Nov. 23.
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AT THE OPERA-HOUSE
The “diamond horseshoes” formed by the boxes at the Metropolitan Opera-House never better deserved their name than Monday evening, when the orchestra, under Dr. Dumrosch’s baton, swung into the opening measures.
   
25 November 1906, Washington (DC) Post, pg. E7:
READY FOR THE OPERA
Social Season in New York
Opens Auspiciously.
HIGH PRICES PAID FOR BOXES.
Aspirants for Social Honors Find Place
in Famed “Diamond Horseshoe” at the
Metropolitan of Equal Advantage to
Owning an Establishment on Fifth
Avenue—Ryan’s New Business Policy.
   
13 November 1917, Chicago (IL) Daily Tribune, pg. 5:
THE DIAMOND HORSESHOE
Boxholders and Their Guests at Opening Performance of Opera.
BOX holders and their guests at the opening of the 1917 season of opera at the Auditorium last night,...
   
28 April 1921, Atlanta (GA) Constitution, “Bits of New York Life” by O. O. McIntyre, pg. 10:
The diamond horseshoe metropolitan is a mute testimonial to the successful New Yorker’s desire to strut. A box costs a fortune a year. The occupants are generally bored to death with operas that they have heard time after time and they come when the performance is half over merely to show their ropes of pearl, tiaras and gowns. The real lovers of music are perched perilously in the gallery.
   
Newspapers.com
28 January 1930, Scranton (PA) Republican, “On Broadway” by Walter Winchell, pg. 4, col. 2:
The MGM ads about “The Rogue Song” refer to the Met Opera House’s “Diamond Horseshoe”...It’s the “Golden Horseshoe,” you dope!
 
23 October 1938, New York (NY) Times, “Night Club Notes” by Theodore Strauss, pg. 162:
In case you’re wondering what happened to Billy Rose’s idea for another night club in the Broadway sector, the clairvoyants predict that Master Rose will open his now spot in the former grill of the Hotel Paramount on West Forty-sixth Street on or about Nov. 25. It will be called the Diamond Horseshoe and will be decorated by Albert Johnson in the lavish manner of the mauve decade.
 
OCLC WorldCat record
The golden horseshoe : the life and times of the Metropolitan Opera House
Authors: Frank Merkling (Author), John W. Freeman (Author), Gerald Fitzgerald (Author), Arthur Solin (Author), Eleanor Robson Belmont, Anthony A. Bliss
Print Book, English, 1965
Publisher: Viking Press, New York, 1965
 
27 May 1966, New York (NY) Times, “Save the Met or Raze the Met?” by Theodore Strongin, pg. 36:
The controversy over the Metropolitan Opera House at Broadway and 39th Street is rising to its crescendo. Many arguments have been expressed for and against saving the 83-year-old building with its historic Diamond Horseshoe, which is now facing the wrecking ball.