[Jim McDougall]

Looking further, in the remarkable work by Richard Dellar, "The British Cavalry Sword 1788-1912"(2013), on pp.2-3 the 15th Light Dragoons swords are noted.
The illustration (1.2) is similar to my example, and is shown as simply a light dragoon sword of the period 1760-70. As I had noted, these units were begun in 1759. We know that Jeffries made an identical sword of the one I have as the example from Royal Armouries is marked by him, and I have suggested that perhaps this type was one of the number produced by him in 1759.

There were however a number of other regiments as light dragoons, so it is possible these swords might have gone to them in degree as well.

In the example noted in Robson (1996), a 15th L.D. sword of 1763, the one with recurved quillons, it appears these were also made by Jeffries, and that while officers seem to have had chiseled lion head pommels on thier hilts, with troopers carrying similar but with these plain pommels. These must be incredibly rare (as noted in the MDL link and the price it sold for).

By 1780, the 15th Light Dragoons had gone to a simple knuckleguard stirrup hilt (illustration 1.3) shown as c. 1780. These swords were considered rare when I acquired one back in the 70s.
We know they were used by the 15th Light dragoons as examples in Dellar have blades made by Cullum (Charing Cross) and were marked 'Kings Light Dragoons' (the regiment official title).

So it would seem that my example may be one of the number of light dragoon swords produced in 1759 by Jeffries, as by 1763 he was producing the recurved quillon type. It is unclear if this regiment used the four slot type with two branches of 1770s, but by 1780, it was the stirrup hilt.

Attached : the founding colonel of the 15th light dragoons,
The two illustrations from Dellar (op.cit.)

The one in Royal Armouries purchased by them 1981. This and the 140 in Belvoir Castle are known, uncertain of others.