A penny of that era measures 34mm in diameter.
A halfpenny measures 25-28mm.
Between 1797 and 1860 British 'copper' coins were minted, as the name implies, from copper; after 1860 they were minted from bronze.
This means that 1860 coins exist either as copper or bronze. Copper coins have the date under Victoria's head and bronze coins have the date under the figure of Britannia. Therefore your coin must be of bronze (a pity since the copper versions appear to be quite valuable).
The coin should also have "ONE PENNY" (or "HALF PENNY") raised about the figure of Britannia as shown
here and
here. If this wording has worn off if may greatly affect the value of your coin.
A guide for values of coins in decent condition can be found here...
http://www.tclayton.demon.co.uk/values/penny.h tml#QV
http://www.tclayton.demon.co.uk/values/halfp.h tml#QV