The 40 francs Napoléon gold coin contains 11.61 g of fine gold (12.90 g at 900‰) — double the 20 francs. Less common than the 20 francs, it can carry a slightly higher premium. Here's how to identify it, estimate its value and sell it at the right price.
Struck mainly under the Consulate, First Empire and Restoration, the 40 francs gold coin weighs 12.90 g at 900‰ fineness, i.e. 11.61 g of fine gold, 26 mm diameter. It contains exactly double the gold of the 20 francs.
Its intrinsic value is calculated as: 11.61 g × the day's gold rate. On top comes a premium often slightly higher than the 20 francs, as the 40 francs is scarcer and sought by collectors. To read the rate, see understanding the gold rate.
Compare several buy-back rates (see how to compare). On a scarcer coin, condition and year matter more: don't clean it and have it appraised if the year is sought after. See also investment gold coins.
By weight they're equal (the 40 francs = two 20 francs). The 20 francs stays more liquid (easier to sell singly); the 40 francs, less common, may offer a small premium but a narrower market. Compare with the 20 francs Napoléon.
It rests on its 11.61 g of fine gold (intrinsic value = 11.61 g × the day's rate), plus a premium often slightly higher than the 20 francs, as the coin is scarcer. Compare several buy-back rates.
It weighs 12.90 g at 900‰ fineness, i.e. 11.61 g of fine gold — exactly double the 20 francs gold coin.
By weight it's equivalent. The 20 francs is more liquid and easy to sell singly; the 40 francs, scarcer, may carry a small premium but a narrower market.