France
Napoleon III gold 100 Francs 1858-A MS64 NGC, Paris mint, KM786.1. An attractive piece that is very coveted in high grades. To give illustration to that point, in September 2014 Heritage sold an NGC MS61 example for $2,100 hammer (Heritage 3035, lot 30521). Yet just a month earlier, the Lissner example, graded MS65, sold for a whopping $27,000 hammer (with a higher buyer's premium as well!). While the piece here is perhaps not quite that fine, it is still very attractive and well above average for the type.
Estimate: 6000-8000 USD