Dolf, that's correct. The few non-military .455 target models had 7.5" barrels and were manufactured four to five years before the first military contract .455s with fixed sights and 6.5" barrels went into production.
The proof marks on the barrel look like the crown-above-BV type, which are one of the many known Birmingham proofs. One in your photograph is legible despite being slightly blurry. The other is more blurred, but looks as though it may be a weakly struck imprint from the same stamp.
As to shooting high, I am not surprised. The front sight on .455s is quite tall on the fixed-sight models that have the in-frame rear notch. The drift-adjustable rear sight has a notch that is slightly higher than the frame notch, so the front sight would need to have a corresponding increase in height in order to maintain the proper impact point of the bullets fired from the revolver. Instead, the front sight is much lower than the standard fixed-sight height. Such a configuration may be appropriate for long-range competitions, but it is a prescription for hitting high when shooting at closer targets. Since the front sight is removable, it can be replaced with a taller sight for use at shorter distances.
Now that I think of it, can you ask your friend to take close-up photos of the front sight from the side, top, and angling down on it from a little above, behind, and off to the side? I'm wondering if it is possible that the site is damaged and that a top mounted white or brass bead may have been broken off.
EDITED TO ADD: I see that Jim got his comments posted first, which often happens when we both want to say something about a specific point. I used to be able to type faster than I do now.
