2 British Pence in 1979 had the equivalent value of about 1 cent USD.
There were no British 1979 20 Pence coins minted.
Your description is applicable to every British coin issued in 1979. On the same side of the coin you read "New Pence", there will be a number indicating "how many" New Pence. The 1979 British 1/2, 5, 10 and 50 New Pence coins have long been withdrawn from circulation and have little or no value unless they are in mint condition, and even then, not much. The 1979 British 1 New Penny and 2 New Pence coins are still potentially in circulation, so are worth 1 and 2 Pence respectively, unless they are in mint condition, and even then, not much.
See the link below.
How much is a UK half pence worth
How much is a UK half pence worth
In 1979, a barrel of oil cost the 2010 equivalent of $74.23 dollars per barrel (in 1979 it was $25.10)
A British 1979 (silver) Twopence (Proof FDC), uncirculated and in absolute mint condition could fetch up to £20 GBP. A reputable coin dealer will be able to give a more accurate valuation.
The equivalent of $1,000,000 in 1979 to todays (2011) standards would be $2,790,000.. 1979 $1= 2011 $2.79
These coins are still potentially in circulation so, unless they are part of a Proof or uncirculated mint set or are individual Proof or uncirculated coins and in absolute mint condition, they are worth 2 Pence. A British 1979 bronze 2 New Pence coin (Elizabeth II), uncirculated and in absolute mint condition could fetch up to £0.15 GBP. A British 1979 bronze 2 New Pence coin (Elizabeth II)(Proof FDC), could fetch up to £1 GBP. A reputable coin dealer will be able to give a more accurate valuation.
The larger pre-1993 10 Pence coins were withdrawn from circulation and demonetised in 1993. So, unless they are part of a Proof or uncirculated mint set or are individual Proof or uncirculated coins and in absolute mint condition, they have little or no value. A British 1979 cupro-nickel 10 New Pence coin (Elizabeth II), uncirculated and in absolute mint condition could fetch up to £0.50 GBP. A British 1979 cupro-nickel 10 New Pence coin (Elizabeth II)(Proof FDC), could fetch up to £2 GBP. A reputable coin dealer will be able to give a more accurate valuation.
Occasionally, the Royal mint has a mix up with the dies or the blanks used to produce coins. It is possible that the 10 New Pence dies were used on a 2 New Pence blank. If this is the case, part of the 10 Pence coin design will be outside the perimeter of the 2 Pence blank, the 10 Pence coin being slightly larger than the 2 Pence coin. Alternatively, you may have a trick coin available from magic shops.
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