7c Junk on the Yellow River with train approved die proof, China, 1922
This junk ship stamp design by American engravers Lorenzo Hatch and William Grant had three printings, the first of which was re-engraved in London. Grant copied the London engraving for the first Beijing (Peking) printing. The second Beijing printing used the original dies. Philatelists study the engraving details to identify the different printings.