May 1851, Genuine #1a,
First printing (by Ferslew)

1.) Engraved burelage
2.) Watermark 111 (small crown)
3.) Hyphen after "Post"
4.) Pointed front on the "2"

Exp: APS certificate

Forgery of #1

1.) Horizontally laid paper
2.) No watermark
3.) No burelage
4.) No hyphen after "Post"
5.) Front of the "2" is blunt

Exp: APS certificate

August 1852, Genuine #1
Second printing (by Thiele)

1.) Typographed burelage (it will not show up in the alum foil test)
2.) Watermark 111 (small crown)
3.) Hyphen after "Post"
4.) Pointed front on the "2"

Exp. do.

    

1866, Official reprint
Facit #1N3

1.) White paper (some, #1N2 and #1N3, are on yellow paper)
2.) Without burelage (some, #1N2 and #1N4 have burelage)
3.) Without gum

Exp: do