A New York Yankees baseball cap worn by Hall of Famer Babe Ruth is going up for auction today, 15 years after its current owner, former pitcher David Wells, donned it for an inning at Yankee Stadium.

Worn by Ruth in the early 1930s, the navy blue flannel cap is worth an estimated $400,000, according to SCP Auctions, which is handling the sale. The auction opens today and closes on May 19, the company said in an e-mailed statement.