I wonder what aspect of the Obverses make you think that they are F 5s , as example one to me looks more like a 6 . All the 5s I have seen have a distinct gap between the back of Victoria's head and the bottom of the left corner of the B in BRITT, where as on the 6s it almost touches the head.
Also both the 5 and 6 have the pinch in top of the ribbon so nothing there to determine the type.
I do think that all three are reverse Fs as the plume is very wide as happens to worn Fs, and the square rock below the shield is faintly visible , and a slight depression to the left of the square rock seems to show.
The example 2 has more chance of being a 5 as the teeth and rim when worn look narrower than on the 6, but the B in BRITT looks to close to the head to be a 5. ?
But then who knows , who could be really certain !!!