Sjoelund
A nice try, thanks, but still not 90° over the center of the coin.
I copied the coins into a rectangle:
Hey Ole, there's a simple solution for this. I think you use PhotoScape v3.7 too, right? The ideal program for cropping, making GIF's etc.
One of the features is also adapt pictures where the aspect ratio is not correct (something often happens with smartphone pictures).
In this case, width is 711 pixels but height is only 668 pixels.

So click on the “resize” button and fill in the same amount of pixels for width and height. Don't forget to untick the “preserve aspect ratio” box and of course save your picture.
The result:

I've pasted the result in your original picture so you can see the actual difference:

I hope this was useful. The explanation takes much longer than the change itself.