Improving a Bad Scan

How to fix (someone else's !) bad scan

What is the first thing that we should do to correct this?

Let's first of all crop it down some more to get rid of the unnecessary black frame.  This is an easy thing to do (!) and also then means that when we look at the brightness levels we'll be getting data more from the stamp and less from the background.

Now for the fun stuff.  Calling up a levels graph shows a dreadful narrow concentration of brightness values.  You can see from the sliders underneath the levels box - or from the values in the text boxes above - how I have moved all three sliders to try and 'punch up' the color and contrast.  I adjusted these levels based on my best guess as to what the blue and white paper colors should be, and suspect that I've probably slightly over-saturated the image as a result, but it does make it more clear.

Making these changes to the image gives us this result :

That looks like someone has removed a veil from the image, doesn't it!  Next, let's see if we can't sharpen it some by using the unsharp mask.

At this point, there isn't much else we can do.  The paper color looks reasonably accurate so there is no need to try and change the color balance, and while the final result is still poor, compare it to the original image and you'll hopefully agree that just a couple of simple changes made a huge difference.  If only the eBay seller had done the scan correctly to start with!