Regarding the framed plaster medallions readerWhitney Allen asked about,Pete Smith writes:

Dassier's Kings & Queens
Jean Dassier of Geneva published a series of 34 medals of the Kings and Queens of England in 1731. They were offered for sale in England at 6 guineas in bronze and 15 guineas in silver. They were also available in damascened bronze with the fields of the medals bronzed and the relief gilded. The dies for the series came into the possession of Sir Edward Thomason, who reissued the medals around 1820.

The earlier medals were struck on slightly thinner flans with slightly beveled edges. They have a finish that is a little duller. The later issues have slightly more reflective surfaces and vary in the color of their patination. Some show signs of die wear and defects. Examples cast from struck medals also exist. They are slightly smaller in size and poorer in quality.

For more information, see:
Dassier's Kings & Queens(https://www.mcssl.com/store/8596432/dassiers-king-queens)

Scott Miller writes:

For more information, see:
KINGS AND QUEENS OF ENGLAND by JEAN DASSIER(http://www.historicalartmedals.com/MEDAL%20WEB%20ENTRIES/
THUMBNAILS/SWISS-DASSIER-KINGS%20AND%20QUEENS/brand%20new%20thumbnails.htm)

Pete adds:

Chris Eimer writes:

Hedley Betts writes:

Intaglio is an Italian word, and the G is silent, so it is pronounced "INTALIO" and it means carved in. It is a depression, much like the head of a Phillips head screw. A cameo is the opposite, it is raised above the surface. Most intaglios are meant to be used to make a cameo image when pressed into clay or wax or other soft medium. Usually an intaglio is in the form of a ring or fob, a carved in family crest that can be used to make a wax or clay seal by pressing the ring into the soft clay or wax. In the Bible when the prodigal son returns, his father says to put a ring on his finger. This was no mere bobble, but a family crest ring which identifies the wearer as a member of the family.

In Egypt, most of the people could not read or write, therefore they could not sign their name. They needed a way to sign their name so small Scarabs were carved with their name on the base carved in intaglio. These small Scarabs had a hole drilled through them and a string was put through the hole and tied around the wrist and the scarab was worn like jewelry. When the owner needed to sign his name, he could press the scarab into a soft clay tablet, and this would be his signature.

In Greece and Minoa, they took intaglio carving to the next level and carved pictures into the stone. Sometimes pictures of warriors, or the king, or lions or whatever but these intaglios took months to carve into the stone using spinning wheels and grinding powders so only royalty or very rich people could afford to own a beautifully carved intaglio.

The Etruscans copied the Egyptian Scarabs but instead of a name on the base, they carved pictures like the Greeks and Minoans. These were usually carved in carnelian agate and today, if you want to own one, prepare to spend a fortune!

When the Romans conquered the Greeks, they saw how great the Greek stone carvers were and so they used them to have their intaglios carved. The roman word for a stone carver who could carve an intaglio was "CAVITOR."

OK, we will skip over most of the dark ages where when people found the intaglios they thought those pictures were put in the stone by God, and they carved little religious symbols into them and gave them to priests and the like.

Now we are up to about the year 1550, life has settled down and in Europe and England life is divided into rich folks and poor folks. The rich live in manor housed and the poor work the land and pay taxes to the rich. The children of the rich folks are well educated and after they graduate college, as part of their education, they are sent on what is called "The Grand Tour." They will spend several years traveling to the great places in Europe such as Paris, Rome, Venice, and Athens. There are no museums, those have not been invented yet, so they stay with other rich folks or royalty and there they see the collections that have been gathered. They want to bring home things that they have seen in Europe! (Hold that thought.")

You have heard the saying "Signed, Sealed, and Delivered." This was literal, your signature on a document was not enough because someone could copy it. You had to have a Seal to accompany the signature. They would melt red wax beside your signature, and you would press your personal intaglio seal into the hot wax leaving a cameo impression of your crest or initials or whatever was carved into your seal. Rich folks had them, poor folks did not, and poor folks were jealous! By the time of the Industrial revolution in the late 1700's, every business, school, church, and gentleman had a personal seal. A man named James Tassie began collecting copies of seals. He would make impressions using melted sulfur mixed with red ochre, and his collection grew to thousands of impressions. This was a time of experimentation and he found that he could make copies of famous old seals out of glass. This was called Vitreous Glass Paste. He sells these and now everyone can own an intaglio. Josiah Wedgwood begins making black clay copies of some of them and calls them Basalt Ware. Later he will make the famous white on blue copies and call them Jasper Ware.

Jump back to Rome where the best seal carvers live and where the rich people are coming on The Grand Tour. A man named Paoletti has been collecting images from seals and he starts making copies of them out of a mixture of ground marble and Plaster of Paris. He puts these impressions in fake books and tourists buy them to take back to England. This is about 1820 now and he scraps the ground marble and uses only plaster of Paris. Some of these got framed and put on the walls of posh houses. People liked collections of things and businessmen such as Wedgwood made sets of images such as Kings of France and Kings of England. Art medals had become popular, but these were expensive. However, plaster copies of art medals were inexpensive and so people would collect plaster copies and frame them. These were usually made with a paper surround with a gilt edge so when you looked at a copy in a frame you saw the white plaster and a gold border. If you owned a large collection of things, you could make plaster copies and sell them. Early museums even allowed collectors to come in and make copies. You will not see that today.

Whitney Allen writes:

To read the earlier E-Sylum article, see:
QUERY: PLASTER MYSTERY MEDALS(https://www.coinbooks.org/v23/esylum_v23n41a13.html)