Freemasons, most likely. I'll see if there is an example in the current bible but the era would be 1850s-1870s. Looks like a Philadelphia Horstmann&Sons assembly but it may not be marked to them, as they sold to other retailers. A peened assembly means it would be a chore to see the tang stamp. There were swords of that period that had cast guards in the form of the skull&bones and all associated with Freemasonry and more so the Scottish Rite Blue Lodge hierarchy. Possibly a lodge Tyler/tiler man at arms vs a Knights Templar.
These forms with the Roman Centurion and plumed knight pommels started with US militia swords evolved from a mix of French 1st Empire pommels and English guards. By the end of the ACW, the general form adopted by many fraternal and military association groups. Personally, I would label this one as ACW period (1861-1865) but it might fall a little bit later. Was this found in one of the Confederate states? There are some Confederate Sons of America (veterans) and KKK swords using the iconography. Looks like there are enough stars to represent the 13 colonies, so I wouldn't immediately jump south.
I promise to check the book
Cheers
GC
Ok, I promised to look. No exact match there but the skull&bone guards I was thinking of are not necessarily of the Blue Lodge group (?) but still Scottish Rite. Most notably the Ancient and Accepted, and, Ancient Free and Accepted Freemasonry groups still under the Scottish Rite umbrella with degrees like any other group. I don't know these things entirely.
An uncle just had a dinner presentation celebrating his 65 years of Freemasonry. Doing well at 90