Plate 6 was manufactured in early 1856 and used continuously until about February 24, 1857, when perforated stamps appeared. All stamps from this plate are Type I, having no inner lines. This plate never showed any significant wear. Approximately 21,211,000 stamps (106,055 impressions) were printed from Plate 6. Refer to Dr. Chase's book The 3¢ Stamp of the United States 1851-1857 Issue for the full story of Plate 6.
Plate 6 - Earliest Use February 18, 1856; Used for 17 Months; 106,055 impressions/21,211,000 stamps/5.85% of issued; 200 Scott 11:
Chase - Plate 6:
Images are provided courtesy of Smithsonian's National Postal Museum