A true piece of basketball history is about to hit the auction block!
Michael Jordan AND Kobe Bryant's first game-worn NBA jerseys will soon be available to bidders at Sotheby's ... with experts estimating the two tops could combined fetch up to $20 million!
TMZ Sports has learned that Jordan's Bulls jersey is from his NBA preseason debut on October 5, 1984 ... where His Airness dropped 16 points at the Peoria Civic Center in Illinois.