it could be a confederate made item (pettibone was New Orleans based I think ) -- union style 1860 staff / field officer model( note the US in the middle of hand guard bow) --- likely made before union troops took over New Orleans -- possibly buried by confederate supporters under the house ...while New Orleans was Occupied by union troops
Lots of copies of this sword were made since Ames designed it in late 1858, it was accepted by the U.S. military in 1860. Very slight variations allowed makers to get around patent laws of the times. This sword was a favorite of many, many lodges, the lodge identification quit often appeared on the scabbard. P.S. Your example appears to have a cast grip, as opposed to a proper wrapped grip, which leads me to believe you have a lodge or military association sword, G.A.R. , etc.