I wouldn’t know whether it was wealthy at the time. It also was a lot larger than it is today (https://en.wikipedia.org/wiki/Partitions_of_Luxembourg#Third_Par

I wouldn’t know whether it was wealthy at the time. It also was a lot larger than it is today (https://en.wikipedia.org/wiki/Partitions_of_Luxembourg#Third_Partition https://en.wikipedia.org/wiki/Partitions_of_Luxembourg#Third...: “The territory ceded to Belgium was 4,730 km2 (1,830 sq mi), or 65% of the territory of the Grand Duchy at the time. The population of this territory was 175,000: half of Luxembourg's total population”) Looking at https://en.wikipedia.org/wiki/File:Europe_1815_map_en.png https://en.wikipedia.org/wiki/File:Europe_1815_map_en.png, the Papal States were a lot larger in 1815 than I envisioned, though, so yes, Luxembourg or San Marino or something else tiny probably would be the ‘winner’.