2-8-4 No. 3389 was selected for the Lima builder's photo of the final group of Berkshires delivered to the Erie. The S-4 class of 20 members was outshopped in 1929 with specifications differing slightly from those of the S-3 class built by Baldwin the previous year. With a higher boiler pressure of 250 p.s.i., they developed 78,904 pounds of tractive effort. Their evaporative heating surface, at 5695 square feet, and superheating surface at 2545 square feet, gave them a total heating surface even greater than that of the Lima-built S-2 class of 1927. At 468,600 pounds they were the heaviest group in the Erie's stable of 105 Berkshires, the pioneering design that spawned the Advisory Mechanical Committee's 2-10-4 and 2-8-4 configurations eventually used by at least six other U.S. railroads.