This is how it is on my PC as well. I am only able to right-click save the reverse of the image. The only thing I can think of would be the script not working properly in IE or maybe not fully executing before the image is saved. I tossed up a pre-loaded image as well and I still get the same results. ( the 50 pence on the left is not pre-loaded )

Unable to try using IE at the moment , but will keep looking into this. The images could still be saved via print screen or right click > inspect element which would give you the filename and then you can just open the file in a new window so you would have to use a combination of both disabling right clicks and watermarks.