cover

The 4¢ Grant stamp was used to pay four times the 2¢ / ounce 3rd class mail rate for a total of 8 ounces.  It is sometimes difficult to distinguish between 1st and 3rd class mail.  There are two "tell tail signs".  One, there is no date postmark used to indicate how quickly (or how slowly) the letter traveled.  The second sign is if the back flap is left unsealed.  An unsealed cover allowed postal employees to inspect the contents to verify that there was no personal correspondence.