The best way to check them if they are on your monitor, is this little trick I figured out. Even on
ebay actions where they like to angle the images, you can always tell:

They are actually to different designs:

Note the inside curl of the '9'? That is the difference that is easy to see:

The curl and the location of the lower part of the '7'. Hope this helps. The floating roof is just an die event, where dies get over polished. To me they are nothing special along with the other missing devices from over polishing.