That is far too expansive a question to be answered in this forum and the detail would go on for pages.
The weight of any given coin would depend on the denomination of the coin, what it is made from, when it was made, where it was made and who the Monarch was at the time.
18th century British monarchs include King William III, Queen Anne, George I, George II and George III.
The dimensions of coins were changed frequently to cater for the uncertain or tenuous financial states of Britain during this period as a result of various wars and other strains on the national economy.
A British coin catalogue covering the period should give the information you require.
In a way.
There was a coin of Scotland that was issued for
the value of 18 Shillings, but it was called a 1 Unicorn,
and was issued by James IV (1488 - 1513).
The first Farthing coins were minted during the late 13th century however, recent finds suggest that they may have minted earlier again in the early 13th century. The first Halfpenny coins were minted during the early 10th century. The first Threefarthing coins were minted during the mid-16th century.
British coins circulating in or around 1562 included - Gold coins - the Sovereign, Angel, Half Angel, Quarter Angel, Half Pound, Crown and Half Crown. Silver coins - Shilling, Sixpence, Groat (Fourpence), Threepence, Halfgroat, Threehalfpence, Penny and Threefarthings.
British copper coins changed from copper to bronze in 1860. Bronze as used in British coins, is more than 95% copper and the addition of a few percent of tin and zinc makes a stronger and more durable coin. The exact percentages varied slightly during the course of the 20th century.
The British decimal Penny weighs 3.56 grams.
This is not as simple a question as it seems it should be. Coins have been used in Britain for over 2,000 years, and produced there for almost as long. The penny probably dates to around the year 1000 AD, although the notion of putting denominations on british coins is a relatively recent innovation (19th century). Also, the first dates on british coins came about in the 16th century - prior to that, the portrait of the king or queen would give you a range of dates during which the coin had been produced.
Mintage figures were not very reliable until the 20th century, since coins were often minted by weight rather than a specific quantity or value. There were about 2.7 million British 1853 Half-Sovereigns minted.
No, they are not rare. British coins were minted that way for hundreds of years. The process is called "Coin Rotation" or "Die Axis". British coins were minted with a 180 degree rotation, so that reverse is 180 degrees out of alignment with the obverse. The practice was gradually discontinued during the course of the 19th century. By 1887, all coins were minted without "coin rotation". Many other countries used "coin rotation" on their coins and not always at 180 degees.
The British "Sovereign" coinage has been minted to a standard specification since the Great Recoinage Act of 1816. In mint condition, the Half-Sovereign is 19.30 mm in diameter and weighs 3.99g.
The copper content of 20th century British predecimal Pennies, Halfpennies and Farthings varied from 95.5 to 97%. When the use of silver in coins was discontinued after 1946, all British "silver" coins were made from a copper-nickel alloy consisting most commonly of 75% and 25% nickel.
No, India has undergone several major changes in their coinage. Inded, some denominations used during the British rule of India no longer exist such as the Anna. The coins used in India today aren't the same size or composition as those used during British rule.
The unimetallic commemorative British Two Pound coins issued from 1986-1996 are heavier and thicker than the later bimetallic Two Pound coins issued from 1997-present. Unimetallic Two Pound coins 28.4mm in diameter 15.98 grams in weight 3.1mm thick Bimetallic Two Pound coins 28.4mm in diameter 12 grams in weight 2.5mm thick
All British sterling silver Crown coins from 1887 to 1902 inclusive are 38mm in diameter and weigh 28.35 grams.