[Jim McDougall]

This is an officers saber of the stirrup hilt M1796 style and appears British, though the squared sword knot fixture on the guard apparently for sword knot seems unusual.
It seems to have been gilt bronze hilt with ivory grip which always seems to suggest naval to me, though there are no fouled anchors apparent anywhere.

This does not automatically exclude naval use, and naval officers often seem to have followed cavalry patterns in fighting swords.

I have attached a similar example from "Naval Swords & Dirks", Sim Comfort, 2008.

I would very much appreciate comments, especially on this curious fixture for sword knot which is different than anything I have seen. The gilt is mostly gone, as is the bluing and gilt motif on the blade.

In "Naval Swords", P.G.W.Annis, 1970, on p.43 (#24) is another similar example, which shows the typical manner of showing the sword knot,in the traditional manner.
As these had become decorative and in many ways status oriented, possible this 'side mount' made for better display of the often highly embellished knots Note that gilt brass was keenly preferred by officers, and they preferred longer blades than the usual hangers or small swords as noted in 'Annis'.
In remarks on this example he notes that when the M1796 cavalry saber was introduced, these were quickly copied by naval officers, and by 1805 a regulation pattern of the type was introduced.

These types with the 'birds head' pommel same as cavalry were likely the early and privately commissioned officers sabers prior to the 1805 pattern.