George IV (George Augustus Frederick) was king of the United Kingdom of Great Britain and Ireland. George IV led an extravagant lifestyle that contributed to the fashions of the Regency era. He was a patron of new forms of leisure, style and taste.
It sounds like you have a gold sovereign from 1827, which is a valuable coin. It could be a half sovereign, because the two coins look alike, only their size and weight are different:
HALF SOVEREIGN: 19 mm diameter, 0.118 troy ounces gold
SOVEREIGN: 22 mm diameter, 0.235 troy ounces gold
The amazing coin in our picture comes from (where else?) GoldSovereigns.co.uk, one of Chard's family of web sites. CoinQuest thanks Chard for use of their coin photo. It is a beauty!
This series of coins runs from 1825 to 1830. To figure value, you must use a two-step process. First, compute the base value (BV) of the coin due to gold content. Multiply the gold content of the coin by the current price of gold. At this writing, gold is selling at $1197 US dollars per troy ounce. (Look it up at kitco.com; prices change every day.) BV of these coins is then:
HALF SOVEREIGN: BV = 0.118 x 1197 = $141 US dollars
SOVEREIGN: BV = 0.235 x 1197 = $282 US dollars
Second, compute catalog value by adding a collector premium to the BV, as follows.
worn: BV + $150 US dollars approximate catalog value
average circulated: BV + $400
well preserved: BV + $800
fully uncirculated: BV + $1400
SOVEREIGNS DATED 1825, 1826, 1827, 1829, AND 1830:
worn: BV + $300 US dollars approximate catalog value
average circulated: BV + $900
well preserved: BV + $2000
fully uncirculated: BV + $3500
Sovereigns dated 1828 are very rare and the value goes to the sky, with catalog values like this:
SOVEREIGN DATED 1828:
worn: $7000 US dollars approximate catalog value
average circulated: $15000
well preserved: $34000
fully uncirculated: $85000
It is best have your coin authenticated, graded, and encapsulated by NGC(click here), PCGS(click here), ANACS(click here), or ICG(click here). Do not use other services.