This is a hard question to answer. But I come up with this. And many coins I own were potential, but in the study of numismatics and eras of coins I just find totally fascinating, we have to visit the reign of good Queen bess, that era of Shakespeare, heart shaped ruffs and codpieces.

This is a 1562 milled sixpence made by Eloi Mestrelle (I have heard 900 kabillion spellings of his name, but I will go with that). He was a French man from the Monnaie de Paris mint and came to England to offer screw press made coins with edges to stop clipping and ensure the right weight of silver meant the coin would pass for its value.
In 1561 the English at the Tower allowed it and milled shillings and sixpences were made. Some were dated, some were not. They went down well and as you can see, even heavily worn, a pretty and very modern looking coin. But it angered the people hammering coins, although helped them lift their game as well, shown below.
They are relatively round and well struck for hammered coins and no doubt it was keeping up with the Frenchman's coines.
But by 1567, the inefficency was showing, the machines kept breaking down and not enough coins were made to sustain production. It did not happen that after years of religious ructions, wife killing maniac rulers and uber Catholics, England had someone with half a brain on the throne and the country prospered, so coin needs shot up and all types of coin needed to be made and fast. Coin hammerers made them well and fast as you can see. Mestrelle slowed down and was fired in 1572. He could not find more work in France and the Netherlands was wracked with a war against its Catholic Spanish overlords, so Mestrelle did what he did best, made more coins, except they were uttered coins and in 1579 he paid the ultimate price.
In 1631 another Frenchman bought milling back, but again it was half hearted, unlike in the 1560s, the hammered coins of the 1630s and 1640s were just awfully made and no one cared as England slid into war.
Finally in 1662 with yet another Frenchman (Peter Blondeau) - England started the slide into total milling with Crowns in 1662, Halfcrowns in 1663 and then the rest of the line up by 1670. Mestrelle had a great idea, it was just he was 100 years too early.
1662 the first year of the modern milled coinage in England. This was a crown

1663 saw the turn of the halfcrown, however striking was an early teething issue as the date is misty. But these 17th century coins are much better examples of milling, higher rims, more durable impressions and even lettering on the edge of the high value coins. The 1562 piece of Mestrelle, has an edge, but its still wafer thin and details wore off fast, plus by 1662 actual screw presses were much better made and more efficient. Not many Mestrelle or Briot coins survive, but Charles II ones do.
I love coins. Especially silver, gold and anything really old.
Member of the Royal Numismatic Society of New Zealand and the Auckland Numismatic Society