Scott 149P3 - National Printing
Original Design - Proof on India
Scott 160P4 - Continental Printing
Reengraved Design - Proof on Card
Scott 138 & Scott 149 - No Secret Mark
National Printing - There is no "C" above the center of the lower right ball
Scott 160 - With Secret mark
Continental Printing - There is a shaded "C" above the center of the lower right ball.
Follow these steps in the identification of your seven cent Bank Note:
There is no need to check for paper type on this stamp since it was not issued for general postage on the soft porous paper of the American Bank Note Company, but you must still check for the "secret" mark. If it has the secret mark it is the Continental Bank Note stamp, Scott 160. This stamp is one of the easier to identify unless a cancellation covers the area in question. The secret mark is quite distinct.
If it does not have the secret mark it is the National Bank Note printing. If the stamp has a grill, it is Scott 138. If it does not have a grill it is Scott 149. 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. If you think your stamp is a grilled Scott 138, you must have it expertized.
Watch for re-perforation (to fake a more well-centered stamp), for re-gumming (a major problem with the Bank Notes), and even for bleaching of the cancellation (to remove the cancel). Unused copies carry a substantial premium over the used stamp.
The Special Printings, Scott 171 and Scott 196, are mentioned here merely for completeness. Only 473 copies, total, of Scott 171 and Scott 196 were sold, and they were never issued for postal use, rather for collectors only. We occasionally see uncertified copies of these stamps offered for sale at ridiculously low prices. You can rest assured that the stamp being offered is not genuine. These stamps are so rare, only 150 copies are known, they seldom come up for sale except in the sale of a major U.S. Collection.