Glen in looking into this further I'm glad you share some of the interest in these unusual and possibly symbolic devices.These have always intrugued me in the swords of this period. As I mentioned there are always potentially Masonic elements which might have been significant to officers who were likely involved in this or other 'orders' during these times. Clearly not only officers who custom ordered swords, but the makers who specialized in thier production may have been colleagues in these groups.
While I discovered a number of basket hilt English swords which used openwork lozenge designs (Mazansky) I also found some interesting other possible connections which could relate. At first I was thinking of the funerary 'hatchment' as used from 17th century with a lozenge shape enclosing achievements of the deceased, but although used in Masonic regalia in thier 'Memento Mori' theme, did not seem pertinant.
There was a compelling connection however in a 'secret organization' which evolved from a group of Freemasons and Protestant militia which clashed with Catholic forces in North Ireland 21 Sept 1795 in what became known as 'The Battle of the Diamond'. The meeting place of the group was at one of the mens home at Diamond Crossroads near Loughall, and called subsequently 'Diamond House'.
While admittedly tenuous speculation, the fact that varying devices of apparant significance seem to have been situated in this openwork bow on the guards of officers swords of this type in this 1790s period suggests that deliberately ambiguous associations may have been at hand. The examples of multiplicity such as several of these lozenges (diamonds) may have been to render the device as simple motif.
This seems to be the case often in Scottish basket hilts, where certain cryptic Jacobite secret symbols became openwork motif in these much as in other Highland material culture. These kinds of possibilities have only been suggested in Whitelaw et al......and in personal discussions with Blair, Mazansky and others but as yet of course, have not been developed.
As always, 'more research to be done'
Best,
Jim