I'm sorry, I've never heard or seen one of these before. Maybe someone here that knows more about these will have an answer for you shortly.
While there are Inverted MM's in the Franklin Half dollar set I don't believe that this is one. If you go to the 2nd pic--- and then stand up and turn your head so you can look at it up-side-down. While it does kindof look inverted if you turned around this mintmark the top would be too long and the bottom too short. No....I think this is a normal MM. Sorry. Speedy