Hi SilverK,

The snuffbox looks to be made in the 19th century and perhaps made in Belgium or France due to the maker's mark lozenge, followed by an unclear, later added import/duty mark ? (Southern Netherlands 1814-1842 or Belgium).
The script I is a Dutch duty mark for unguaranteed standard of fineness new gold and silver objects of national origin used 1906-1953. This mark was used on all new Netherlands silver objects below legal standard of fineness, those with non-precious metal additions, and new heavily silver plated objects, as long as the average precious metal content after melting with the base metal was at least 250/1000. It was also struck on rejected objects which had been submitted at lowest legal standard of fineness. In that case the maker had to choose between destruction or unguaranteed marking.
This mark was sometimes mistakenly used on old and foreign objects and in 1927 also used on objects of old national origin.
Best,
Oel.