I'd vote for it being a modified Petzval. As this page from the 1890 Ben. French Catalogue (found here, thanks to Dan Colucci) clearly states, photographers have pernicious habits of taking lenses apart and screwing them up! There were many variations on the design tried by lens-makers during the 19th century. http://www.antiquecameras.net/petzvallens.html has extensive material if you're interested.