Hi Jim, my squareback 1851 was manufactured in 2016. Something I noticed about the squareback compared to an 2014 Pietta 1851 with the grip tail is that handling the squareback isn't as secure as the 1851 with the grip tail. Also, that squareback trigger guard will be a PITA when shooting compared to the rounded trigger guard. The squareback may have made sense on the larger grip revolvers where used, but it isn't a well proportioned as the rounded trigger guard for the 1851.
IMO if you are looking for display pretty 1851, get the squareback, but if you want a shooter 1851, get the rounded trigger guard revolver.