It has been pointed out to me that I have made an error; department 95 at the period was Vienne, which had one assay office in Poitiers (until a second was opened in Chatellerault 1824 to accommodate the many cutlers who worked there and whose silver-bladed fruit and dessert knives are a particular fascination of mine). Seine-Inferieure was department 86 at the time, and was not 95 until the 1809 cycle of marks. (A rather embarrassing mistake, as I have for some time been working on a comprehensive list of 19th century French assay offices, their marks and dates of operation. Mea maxima culpa.)
Again, sadly, the standard reference for the Poitou-Charentes region, Elie Pailloux's Orfevres et Poincons XVII - XVIII - XIX: Poitou, Angoumois, Aunis, Saintonge does not show this maker's mark. Being familiar with silver knives of the region, I do know that crudely-cut, unrecorded maker's punches such as this are not uncommon in the early 19th century Poitou-Charentes.