"Brass Ring"

[Shapiro, Fred]

I am moving to a new house and my books, such as the Historical Dictionary of American Slang, are packed up (and I'm on vacation, so I'm not near a library either).  Can anyone with better access to HDAS and other sources help me with this query:  A professor has asked me for information on the expression "grabbing the brass ring," and I would welcome any information about early usage of this and theories about its derivation.

Fred Shapiro

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