Beware of Autopens...

On the left, an autopen from Charlie Duke, and on the right a real autograph.

What is an autopen?

An autopen is an automatic signature, made by a "mechanic pen", which in the past learn how the astronaut signs, and then apply this same signature in many items.

How to identify an autopen?

There are many ways to identify an autopen. The first important thing is to know how is the most common autopen signature looks like. If the other signature is exactly the same, then it is an autopen. Some astronauts have 5 or more autopens, so, even autopens can be diferent from one another. Fortunatly, there are a few ways to identify an autopen, here are the most basic rules to follow:

Autopens are uniform in thickness and pressure (usually, bold and black marker):

Autopens often will look "shaky":

Autopens will look exactly the same (unless, different templates are used, like these):

Around the signature, you will see that the paper seems yellowish:

Autopens are mostly never inscribed (autopen on left, real one on the right):

Are they worth anything?

Well, they are a bit like the "space fillers" for the stamp collection. They do look pretty on a flight date cover, and at least they give you an idea of how the real astronaut signature looks like. Here is a good example, a fine Apollo 16 cover with an autopen from John Young. An original one could sell for well over $300, but this one is worth around $5.

Most common autopens

Almost any classic astronaut has at least 2 or 3 autopens. Not to mention the times they send back "secretarial" signatures, in that case, it is a bit more dificult to distinguish from a real autograph, because they are also made by a human hand, and not by a machine.However, there are some autopens that are very common and easily detected, as this one from Ken Mattingly:

Notice the "K" has that little "leg" on the top, comparing to an original autograph, on the right.

But for a complete collection of autopens, you can visit these websites from other collectors:

http://www.geocities.com/Hollywood/Set/7962/apguide.htm
http://www.geocities.com/CapeCanaveral/Lab/4555/autopens.htm