Yeah - my mistake. They are crossing at what? 20 yards? Good elevation, though. LOL.
The rear sight appeared to be the one used on "Remington Zouave" .58's back in the 70's.
The front sight was a not very well made brass blade (too high) in a brass base, dovetailed into a very high modern rifle front sight base.
Rifled 28 bore barrels would have been something over .55 calibre ie: + the depth of the rifling.
My chart shows 28 bore as being .55".
Today, we call .54" smoothbores, 28 bore usually.