There should be 3 pieces of glass. The one in the 5th picture is the front cemented doublet and should 'point' towards your subject. From the photos, it looks like you are missing the third lens element, but maybe I'm mis-interpreting your photos. There should be a thick front doublet, a thinner rear piece, and an even thinner and more bowed piece, usually with a metal ring between the back two pieces. If there aren't 3, it either isn't a petzval (and it should be a Darlot gem from the look), or you don't have it all.

Richard