Mr. Armstrong stopped signing autographs in 1993. As a result, his autographs are rare, highly collectible, expensive, and often forged. As many as 90% of Armstrong autographs available for sale may in fact be fake.
An autograph that is even and perfect is likely a stamp or autopen. A real autograph should have lighter and darker areas as the hand applies uneven pressure.
Using a magnifying glass, you should be able to see tunnels or bridges where ink lines cross.