It certainly difficult to be sure as to whether its a 4 or 5 , but I would favour a 5 as the outer ribbon just below the bow narrows sharply on a 5 ,and they have an in cut groove forming a fold , not to be found on the 4. The narrowing is still clear, but the fold has worn away on this example . As to the over letter, i'm not convinced, its quite common for a die crack to appear around the legend at the bottom or the top of the lettering , and if it were a crack , with the extreme ware present on this example it would not now show as that part of the coin has worn away ??