Crown Over TG Thomas Gill?

[Bryce]

G'day GC,
Radboud is correct that after 1796, crown over number inspection stamps don't correspond to any particular maker. Prior to this they are relatively uncommon, so I don't know for sure, but I suspect that they also don't apply to any particular maker. As to your sword I agree it certainly predates 1796. We know that Henry Osborn used a crown over HO to mark his early swords, so I think it likely that your crown over TG was used by Thomas Gill. As another example, swords from a similar period can be found with a crown over GR over JEFRIS for Jeffries. So no absolute proof, but very likely to be Thomas Gill.
Cheers,
Bryce