Nice coin, Jean. You probably have a gold ducat. These small gold coins contain 0.11 troy ounces of gold. In addition to their bullion value, they carry valuable collector appeal especially if in good condition like yours.
To estimate ballpark value, start with the base value of gold content. Go to a web site such as kitco.com and find the current price of one troy ounce of gold. (Note: when talking about precious metal, 'troy ounce' and 'ounce' are the same, the 'troy' is understood.) Then multiply that price by 0.11. This gives the base value. Currently gold is selling at $1400 US dollars per ounce, so each coin has a base value of 0.11 x 1400 = $154.
Next add a premium for collector value, roughly like this:
worn or damaged coin: add $0
average circulated: add $0
well preserved: add $20
fully uncirculated: add $75
Jean's 1848E is a common date and mint mark for this series. There are a several coins that are worth more than this.
Add an additional $50 premium for the following coins in average circulated condition and up:
Coins dated 1842 through 1846 with the V mint mark catalog for $125 above base value when average circulated, and above $1000 when fully uncirculated.
Coins dated 1841V, 1847V and 1848V catalog for $200 above gold value when average circulated, and $600 above gold value when fully uncirculated.
The *big one* in the series is the coin dated 1840V, which catalogs for $500 above gold value when average circulated, and $1200 above gold value when fully uncirculated.