Napoleaon III, 10 Franc
Marcin Walusiak sent in the images of this coin and asked what it would be worth. It’s a French 10 franc gold piece of Napoleon III.
The coin is dated 1857 and has on the obverse the head of Napoleon III. On the reverse is the denomination with a letter A below, which tells me it was struck at the mint situated in Paris.
Napoleon III was the nephew of the more famous man of the same name, who died in 1821 aged 51 whilst in exile on St. Helena. Napoleon III was President of France from 1848 to 1852 and Emperor from 1852 to 1870. He eventually fell from power after France suffered an ignominious defeat in the Franco-Prussian war and died in1873.
The weight of an 1857 10 franc piece when first struck is 3.2258 grams, the diameter is 19mm and they are .900 fine (900 parts pure gold out of a 1,000). The total mintage of this denomination during 1857 was roughly 14.5 million.
Valuation
In terms of its value, a similar coin recently sold on ebay for £123.