Hi Deb -- You probably have a well-worn 8 reales coin from the old Republic of Mexico.
These coins contain 0.786 troy ounces of silver. So that sets the minimum value they can attain. For instance, if silver is selling at $12 per troy ounce (look it up for today's price at kitco.com), the minimum price is 0.786 x 12 = $9.40.
Coins with the liberty cap and starburst pattern were minted in smaller denominations than 8 reales. In fact, denominations of 1/2, 1, 2, and 4 reales look the same, only smaller. The denomination appears explicitly on the coin in the place where '8R' appears on the 8 reales. Look for '1/2R', '1R', '2R', or '4R' on your coin and, if you have one, click to this appraisal page.
The general progression of catalog values for most dates of the 8 reales goes like this:
worn: $25 US dollars catalog value
average circulated: $50
well preserved: $70
but, these old 8 reales from Mexico have a long history. The further back you go, the more valuable they get. There are several variations of this coin and some of them can be quite valuable, cataloging for $100s of US dollars even in worn condition. There is an elaborate system of mint marks and initials. Coins worth $100 or more in worn condition are shown in the list below. Some of these are quite valuable, tipping the scales over $1000 when in uncirculated condition. Worn coins do not reach this high.
1823 - 1825
1825 - 1831 initials FS
1826 mint mark Zs, initials AV and AO
1827 - 1828 mint mark Go
1828 mint mark Pi, initials JS
1828 - 1830 mint mark EoMo
1832 mint mark Ca, initials MR and AM
1833 mint mark Mo, initials ML
1838 - 1839 mint mark Ga, initials JG and MC
1843, 1845, 1847 mint mark Ga, initials JG
1844 - 1852 mint mark GC
1846 - 1854 mint mark C or Cn
1848 - 1854 mint mark Do
1851 - 1855 mint mark Ca, initials RG
1851 - 1858 mint mark Pi, initials MC
1863 - 1867 mint mark Ho, initials FM
1864 - 1865 mint mark A, initials PG
1864 - 1867 mint mark Do, initials CP
1865 mint mark Zs, initials MO
1865 - 1867 mint mark CA, initials JC
1873 mint mark O or Oa, initials AE
1875 mint mark Do, initials JH
1880 mint mark Do, initials TB
1883 mint mark Ho, initials JA
If you have one of these, seek out a knowledgeable collector or coin dealer for an in-person appraisal.