X0306 4/A 2021-05-12 2021-05-20 0 0001561627 ExOne Co XONE 0001049495 ROCKWELL S KENT 127 INDUSTRY BOULEVARD NORTH HUNTINGDON PA 15642 1 0 1 0 Common Stock, par value $0.01 2021-05-12 4 A 0 5000 0.00 A 40000 D Common Stock, par value $0.01 2021-03-16 5 G 0 E 57562 0.00 D 4175493 I See Footnote Grant of restricted stock under The ExOne Company 2013 Equity Incentive Plan. 100% of the restricted stock vests on May 11, 2022. Mr. Rockwell is the beneficiary of the S. Kent Rockwell Revocable Trust, which is the indirect, sole stockholder of Rockwell Forest Products, Inc., which is the record holder of the listed shares. This Form 4/A corrects the number of shares of restricted stock granted on May 12, 2021 and voluntarily reports early a gift of shares beneficially owned by the reporting person. /s/ Loretta L. Benec, attorney-in-fact for S. Kent Rockwell 2021-05-20