The subsequent high resolution scans are provided so as you read the text describing the “secret marks” added to numerous denominations by the Continental Bank Note Company, you will have an example to refer to (scans by J.H. Barwis, montage by C. DiComo). Please click the image below to enlarge.

The National Banknote Company

The one cent Franklin was issued by all three bank note companies in a shade of ultramarine or blue. The portrait was based on a marble bust by Rubricht.
The NBNC printing with grill was the first to appear, with 9 April 1870 its earliest known use. It was printed on hard white wove paper in ultramarine with pale and dark ultramarine shades also found. It can be found with both the H and I grill. Approximately 5 million grilled stamps were produced and can be found with black, blue, red and green cancellations.
Approximately 140 million of the without grill stamps were printed. The primary color is also ultramarine and pale and dark ultramarine shades also exist. The earliest known use of the without grill issue is 7 June 1870. The without grill stamp can be found with black, blue, ultramarine, magenta, purple, brown, red and green cancellations.

A marble bust by Powers was used as the basis for the two cent Jackson stamp. It was printed in a shade of brown by the NBNC and CBNC. In 1875, the CBNC changed the color to vermilion and the ABNC continued with vermilion when they assumed the contract in 1879.
The National Banknote Company

The two cent Jackson without grill was the first to appear. Its earliest known use is 11 June 1870 in red brown by the NBNC. Pale and dark red brown shades are known. Around 250 million were issued. Black, blue, purple, red, green and brown cancellations have been found.
The earliest known use for the grilled issues is 22 August 1870. Both the H and I grills can be found. About 10 million were produced. Black, blue, red, brown and green cancellations are found.

Houdon marble bust was the source for the Washington design. Originally, Washington was the subject for the three cent stamp. However, in 1883 Congress lowered the rate to two cents and the two cent Washington was introduced to ensure that a stamp bearing Washington portrait was available for the first class rate. The ABNC was the only printer to produce two cent Washingtons.
All three banknote companies produce three cent Washingtons in shades of green. The ABNC also produced one in vermilion.
The National Banknote Company

The without grill version of the three cent Washington has an earliest known use of 1 March 1870. It was printed in green with pale and dark green shades also found. About 1.2 billion were issued. Cancellations can be found in black, blue, purple, magenta, brown, red, ultramarine and green.
The grilled version also in green with pale, yellow and deep green shades has an earliest known use of 24 March 1870. It can be found with both the H and I grills. Approximately 50 million were printed. Black, blue, purple, magenta, red, orange, brown and green cancellations have been found.
In 1883, the four cent Jackson was the last value added to the Banknote series to pay the double weight letter rate. It was only printed by the ABNC.
Unlike most of the other portraits in the banknote series, the five cent Taylor is based on a daguerreotype. No NBNC five cent stamps were produced. The need for a five cent stamp was created with the advent of the UPU in 1875. The rate to foreign countries, who were members of the UPU, was set at five cents; and, therefore the need for a five cent value was created. In 1879, when ABNC took over the printing contract the five cent Taylor continued to be produce until it was replaced by the five cent Garfield.
A presidential assassination gave rise to the five cent Garfield which replaced the five cent Taylor in 1882. The plan was to issue the stamp in black but President Garfield’s widow objected to the stamp in black and suggested brown. Again, like the five cent Taylor the design was based on a photograph. Thus both five cent stamp subject portraits were derived from photographs instead of marble bust like all other portraits in the series.
A marble bust by Volk became the model for the portrait of Lincoln on the six cent bank notes which were printed by all three companies.
The National Banknote Company

The NBNC printed a grilled version in carmine with pale and rose carmine shades also found. Both the H and I grills can be found on this stamp. Only 400,000 are thought to have been issued. Black, blue and red cancellations have been identified.
The without grill version is known to have been used as early as 28 March 1870. Over 27 million were issued in carmine with dark carmine and rose and brown carmine shades also identified. Cancellations in black, blue, purple, violet, brown, red, ultramarine and green are known.
The original requirement for the banknote series did not include a seven cent value. However, in 1870, a treaty with the North German Confederation was concluded which allowed letters by direct steamer at seven cents. This rate was reduced to six cents the following year, but a new seven cent rate to Germany and Austria by Prussian closed mail via England took effect on 1 October 1871. Later the rate to Denmark (1872), Hungary and Luxemburg (1873) were set at seven cents. The seven cent stamp became obsolete in 1875 with the establishment of the UPU. The seven cent Stanton was only produced by the NBNC and CNBC.
The National Banknote Company

The seven cent Stanton with grill produced by the NBNC was the first to appear. Its earliest known use is 12 February 1871 and the H and I grills can be found. Only 120,000 were issued in vermilion with a deep vermilion shade also known. Black, blue, purple, red and green cancellations are found.
The without grill version has an earliest known use of 11 May 1871. It has the same colors as the grilled version but was issued in a considerably larger quantity, a little over 2.8 million. Cancellations in black, blue, purple, ultramarine and red are known.
The marble bust by Powers serve as the model for the ten cent Jefferson. The ten cent value was printed by all three banknote companies.
The National Banknote Company

The grilled version printed by NBNC earliest known use is 2 June 1870. It only is found with the H grill and is brown in color with yellow brown and dark brown shades also found. It is estimated that 80,000 were issued. Cancels of black, blue and red can be found.
The without grill version is found in the same colors as the with grill version but is much more plentiful with over 10 million printed. Black, blue, purple, magenta, ultramarine, red, green, orange and brown have been sited.
The model for the twelve cent Clay was a bust by Hart. The Clay was only printed by the NBNC and the CBNC; however, the ABNC did produce a special printing.
The National Banknote Company

The grilled version of the twelve cent Clay has an earliest known use of 10 February 1870. It was printing in dull violet and is only found with H grill. Only about 10,000 were printed. Black and blue cancels are known.
The without grill version earliest known use is 9 July 1870. It was also printed in dull violet. About 3.9 million were printed. Cancellations in black, blue, magenta, red and green are found.
Clevenger bust server as the model for the fifteen cent Webster stamp. All three banknote companies produced Webster stamps.
The National Banknote Company

The NBNC produced a grilled version of the stamp which has an earliest known use of 2 June 1870. Around 80,000 were issued with the H grill only. The color is orange with bright and deep orange shades also found. Black, blue, purple, red and green cancels have been found.
The without grill version was printed in bright orange with a deep orange shade also found. 24 September 1870 is the earliest known use. About 5.5 million were issued. Cancellations in black, blue, magenta, ultramarine and red are known.
The design for the twenty-four cent Scott was taken from a bust by Coffee. The twenty-four cent value is probably the rarest of the banknote series. While it was printed by the NBNC and CBNC all but one copy has been identified as a NBNC printing. The ABNC only provided a special printing.
The National Banknote Company

The earliest known use of the twenty-four cent stamp is 11 July 1870. This was the with grill version and it is believe that only 2,000 were produced. All have the H grill. The color was purple and dull purple is also found; but most copies have faded over time. Cancellations are only known in black.
The without grill version has an earliest known use of 18 November 1870. It is also purple in color. Finding the color as issued is very difficult due fugitive quality of the ink particularly due to light. A little of 1 million were issued. Cancels in black, red, blue and purple can be found.
The thirty cent Hamilton was produced by all three bank note companies based on a marble bust by Cerrachi.
The National Banknote Company

The NBNC produced a grilled version in black or full black. Only the H grill was used on the thirty cent value. About 20,000 were produced and cancels of black, blue and red are known.
The without grill version is also in black or full black. A little under 900,000 were produced and the earliest known use is 31 January 1871. Black, magenta, red, brown and blue cancels have been noted.
The high value in the series was based on a statue by Walcott. It was initially printed in shades of carmine by all three banknote companies before the ABNC changed it to purple late in the series.
The National Banknote Company

The NBNC produce a ninety cent version with the H grill in carmine or dark carmine. About 28,000 were produced. Black, blue and red cancels are known.
A version without grill was also produced with an earliest known use of 1 September 1872. There is no identified secret mark so distinguishing NBNC printings from CBNC printings has to be done by color. Those that appear to have a bluish tint are generally regarded as being produced by the NBNC. Approximately 185,000 were produced. Black, blue, purple, magenta, green and red cancel have been found.
- Scott Specialized Catalogue of U. S. Stamps and Covers, 1999
- The 19th Century Postage Stamps of the United States, Vol 2, Brookman, 1947
- The Micarelli Identification Guide to U. S. Stamps, Micarelli, 1991
- The Banknote Issues of the United States Stamps 1870-1893, Brookman, 1941
- Cancellations and Killers of the Banknote Period: 1870-1894, Cole, 1995
- United States Two Cent Red-Brown of 1883 to 1887, 2 volumes, Willard, 1970
- The United States Three Cent Green: 1870 to 1887, Wiley
- U. S. 1887 3c Vermilion, Davis, 1922
- The Seven Cent Vermilion United States, Sampson
- The United States Fifteen Cent Stamp of 1870 to 1890, Weiss, Jr, 1995
Secret Marks of the Bank Note Issues