35mmpistolI am not an expert on this pack but it has the zipper to make it a panel loader with some interior pockets. This company does not normally do interior pockets and usually has top loading (or top combined with a zip). And the big exterior pocket is not like any of their other packs. They specialize in hunting packs so they usually worry about spotting scopes and the tripods that go with it.
I assume a photographer had a custom pack designed for that purpose and they decided that maybe there were other folks who might want something like this.