Before the installation of steam coin presses around the later part of the 1700's most denominations had a slightly irregular shape and although the weights were uniform, often the exact sizes were not. During the reign of George III particularly forgery was rife, in fact it played a big part in providing the masses with money for small transactions when regal coinage was thin on the ground. However, the forged coinage was often underweight and under (or even over) sized. For this reason you shouldn't try to be too accurate when concerning some of the earlier coins shown on the table below. 

How do you know if the coin is British?

Most British coins do not state Great Britain, UK, England or any country name. If the legend contains Britt, Britannia, Britanniar or Britanniarum, that's a good indication the coin is British or British colonial (the colony names are nearly always stated). Britannia (and its variations) was the name given to Great Britain by the Romans and has been used on many British coins ever since. The word 'Britt' is in fact part of the King or Queens title, normally you will see BRITT:OMN:REX which is an abbreviation for King of all Britons. (this title was dropped in 1953 after most of the colonies gained independence). 

It is probably also worth bringing up 'HIBERNIA' coins at this stage as particularly during the reigns of George III and George IV (1760-1830) the whole of Ireland was officially part of the Kingdom of Great Britain and Ireland, and coins were minted in London and issued for use in Ireland with the Latin 'HIBERNIA' on them. These coins were often very similar in size to the 'BRITANNIA' coins but sometimes included different denominations and have not been included on this page.

Here is a short guide to help identify British coins dated from 1760 -1967 using metal types, date ranges and diameters. I have not included countermarked coins, proofs or patterns.