There were two British monarchs in 1603:
Queen Elizabeth I of England, Ireland and Wales, who died on March 24, 1603
and King James I (who had also been King James VI of Scotland for several years prior), who acceded to the English throne on Queen Elizabeth's death.
While there were certainly many coins in circulation in 1603, and several coins produced in that year (Largely, if not exclusively, with James' portrait), there do not appear to have been many coins produced that were dated 1603.
The only English coin that I'm aware of that is actually dated 1603 is the sixpence, a silver coin with a portrait of James I. It is valued (according to the Standard Catalog of World Coins) at US$40 in Very Good condition, US$80 in Fine condition, US$250 in Very Fine condition, and US$600 in Extremely Fine condition. As a hammered coin, however, it is difficult for the non-expert to accurately judge the coin's condition.
There were also a few Scottish coins dated 1603:
1/2 Sword & Sceptre - 2.045 grams, 91.7% gold, 0.0603 troy ounces AGW (Actual Gold Weight)- valued at US$350 in Good condition, US$700 in Very Good condition, US$1500 in Fine condition, US$3000 in Very Fine condition, and US$4500 in Extremely Fine condition
1 Sword & Sceptre - 5.09 grams, 91.7% gold, 0.1501 troy ounces AGW - valued at US$250 in Good condition, US$400 in Very Good condition, US$800 in Fine condition, US$1600 in Very Fine condition, and US$3500 in Extremely Fine condition
1/8 Merk - 15mm, 0.85 grams, 91.6% silver, 0.025 troy ounces ASW (Actual Silver Weight) - valued at US$75 in Very Good condition and US$185 in Fine condition
1/4 Merk - 20mm, 1.70 grams, 91.6% silver, 0.0501 troy ounces ASW - valued at US$35 in Very Good condition and US$175 in Fine condition and US$450 in Very Fine condition
1/2 Merk - 28mm, 3.40 grams, 91.6% silver, 0.1001 troy ounces ASW - valued at US$40 in Very Good condition, US$110 in Fine condition, and US$275 in Very Fine condition
1 Merk - 32mm, 6.79 grams, 91.6% silver, 0.20 troy ounces ASW - valued at US$35 in Very Good condition, US$130 in Fine condition, and US$375 in Very Fine condition
A 1601 English Crown comes from the Seventh Issue of coins of Elizabeth [I].
An English 1601 sterling silver Crown (Elizabeth [I]), depending on the variant, circulated but still in good condition, might fetch anything from £1,350 to £7,000 GBP.
The values quoted are the best possible for the best specimens in their grades, but may be significantly lower due to varying demand for the coin and the prevailing economic climate. A reputable coin dealer will be able to give a more accurate valuation based on inspection of the coin and a positive identification.
The last British Farthing was minted in 1956.
The last British Half-Farthing coin was issued in 1868.
The farthing was last produced in Great Britain in 1956.
All British 20th century Farthings were made from bronze. If you have a gold Farthing, it is because somebody has plated it. Modified coins have no collector value.
All British 20th century Farthings were made from bronze. If you have a gold Farthing, it is because somebody has plated it. Modified coins have no collector value.
Such a coin does not exist. The Royal Mint produced no Farthing coins in 1870 or 1871.
There were no British Farthings minted from 1776 to 1798 inclusive.
There were no British Farthings minted from 1808 to 1820 inclusive.
Such a coin does not exist. The last British Farthing was minted in 1956 and they were demonetised in 1960.
Such a coin does not exist. The Farthing was last issued in 1956 and withdrawn from circulation and demonetised in 1960.
Farthings were made from bronze. If you have a silver Farthing, somebody has plated it and it is subsequently of no value as a collectible.
Farthings were made from bronze. If your Farthing appears to be gold, somebody has probably gold plated it. Modified coins have no collector value.