on a 1796 the grip should be ribbed, tho the leather cover seems loose, is the wood underneath ribbed or cord wrapped to provide ribbing? the portion of the back strap that is riveted to the grip wood (the ears) meets the rest in a rather rounded fashion, compared with the above 3 documented originals, where the same bit has fairly squared corners at the transition.
there were some variances in privately made officers models, which could have been a bit lighter.
as noted pics of the whole sword, blade, & scabbard & the markings would help.even the drag at the end of the scabbard can be diagnostic.
p.s. - the rounded ear junctions look more german than british, see
This Linky which is in german, they hilight similar ear/backstrap and other differences between the german 1811 and later ones... (1831 left, 1811 right)
there are notes i found on later model german sabres of similar design to the 1796 UK one being passed off as 1796's. the german 1811 'blucher' sabre which mimicked the 1796 had later descendants. there is a 'lighter' argentinian variant on the site i linked to. could be the scabbard is a mis-match, tho it seems to fit, or it could have been later stamped in an effort to deceive.
on a historic note, the 14th LD did not participate in the waterloo campaign, as they had been dispatched to america to thrash the unruly colonists at new orleans on jan 8th 1815. their results were not quite what they'd expected. i imagine it took them a while to get over it.