The rarest are those made between 1912 and 1914. Without autographic door and stylus, these have a smooth camera back except for the circular access/red window port. The cameras from this earliest 3 year period have the following words engraved on the front lens plate below the lens
VEST POCKET KODAK
PATENTED MAR. 4,1902
OTHER PATENTS PENDING
The Vest Pocket Autographic camera was introduced in 1915 and continued until 1926. The earliest of these have the following words engraved on the front lens plate VEST POCKET KODAK
MAR. 4, 1902, MAY 6, 1913
Later autographic cameras have a smooth front plate with patent details engraved on the rear circular access port cover. VPK Special cameras with crackle finish or Morocco leather covering always had their patent details engraved on the access port cover.