Determine the color of the stamp. If it is reddish brown it is most likely a National Bank Note printing, but you should still check for the "secret" mark. In general, the Continental printings are not as rich as the National printings. Many dealers sort these stamps by color alone.

Note that the somewhat subtle secret mark is often hard to distinguish on the two cent Jackson. Some Continental printings show this added "smudge" of color clearly while others show no trace. These stamps are usually sorted by color unless the presence or absence of the secret mark is obvious.

Scott 135 and 146 - There is clearly no color joining the line and ball to the left of "U.S." Note that the types can also be distinguished by the color. The Nationals are nearly always a reddish brown. This is a difficult issue to differentiate.

Scott 157, 178 and 183  - There is a very light amount of color joining the line and ball to the left of "U.S."  Since the secret mark does not appear on all Continental printings, this stamp must be distinguished by the color. The Continentals are nearly always a brown or dark brown.  Scott 178 and 183 are orange and should not present a problem.

If it is fairly certain that the stamp is a National printing you will need to check for the presence of a grill. If the stamp has a grill, it may be Scott 135. If it does not have a grill it is Scott 146. Care must be taken when authenticating the grill. Many fake grills have been added over the years in an attempt to increase the value of the stamp. Scott 135 is common enough that it may not be necessary to certify all copies, but nicely centered, fault-free, and particularly unused stamps should be certified.

If the two cent stamp is brown or dark brown it is most likely a Continental Bank Note printing, but you should still check for the "secret" mark. If it clearly has the "secret" mark and is on the hard white paper,  it is a Continental, Scott 157. If the stamp is vermilion, i.e. orange, it has the secret mark and may be either Continental or American. Study the vermilion two cent Jackson's to get a feel for the difficult secret mark on this stamp. Check the type of paper it was printed on, if it was printed on the "hard white" paper it is the Continental Bank Note printing, Scott 178. If it was printed on the "soft porous" paper, it is the American Bank Note printing, Scott 183. Remember: all orange two cent Bank Notes provide an excellent chance to look for the "secret" mark, since they must have one, however weak.

If you are unsure of the type of paper used or the secret mark, you should assume that the stamp is the more common variety. If the stamp is unused and has at least partial gum, it should be certified to ascertain the printer, since the value of the stamp will in most cases far out weigh the cost of certification.

Watch for addition of the secret mark by drawing it in (since the Continental printing, Scott 157, brings a slight premium). Watch also for re-perforation (to fake a more well-centered stamp), for re-gumming (a major problem with the Bank Notes), and even for bleaching the cancellation (to remove the cancel). The National stamp is sometimes embossed with a grilling device to fake the scarcer grilled stamp, Scott 135. This does not present too much of a problem on the used stamp since the value multiplier is not that great, but great care must be taken when purchasing the unused stamp.

We include the "Special" printings in the identification guide merely for completeness. Only 416 copies total of Scott 168 and 193 and only 917 copies total of Scott 180 and 203  were sold, and they were never issued for postal use. All were issued without gum. We occasionally see uncertified copies of these stamps offered for sale at unusually low prices. You can rest assured that the stamp being offered is not genuine. These stamps are so rare, only about 173 copies are known, they rarely come up for sale, except in the sale of a major U.S. Collection and are almost never found unidentified.