The New Navy had only been out a couple of years. It must have been considered pretty innovative and progressive, being a side-swing double-action revolver with simultaneous ejection. Perhaps Colt thought so. Maybe they were using the pair of illustrations to show off the features of their newest design.I don't know on that date...but...
On the right side, they have the 'New Navy' DA Revolver represented twice ( instead of maybe having the 'New Navy' and, the 'New Army' being each shown once ).
Otherwise, the year "1856" does not correspond to anything I know of.