Mudlarking: Seal the Deal

wax seal intaglia

By Jason Sandy

Ship IntaglioWhile taking a well-deserved break from his archaeological studies at University College London, Alan Ross made an amazing discovery as he walked along the River Thames at low tide. On a day he will never forget, Alan spotted something which resembled a cough drop laying on the surface of the exposed riverbed. When he picked it up and turned it over, he discovered that a ship with rowers was delicately carved into the convex surface of a brownish-red, semi-precious carnelian gemstone. The extraordinary object is a Roman “intaglio” (engraved gem) depicting a rowing galley with a figurehead of a goose or swan.

Carved with various motifs, intaglios were typically made from semi-precious gemstones or glass which were mounted in signet rings or a seal matrix and used to stamp, authenticate and seal official documents or letters. After placing a blob of thick, melted wax on a document, the signet ring was pressed into the soft wax, leaving the impression of the intaglio which contained the personalised symbol of the owner. The recipient of the document would recognise the unique symbol which proved the authenticity of the document.

The cutting and style of Alan’s intaglio indicates that the stone was probably carved in the 3rd century AD, and the nautical illustration could refer to the Classis Britannica, the British fleet of the Roman navy which controlled the English Channel and waters around the Roman province of Britannia. According to Alan, it is possible that the intaglio “could have belonged to a captain in the Classis Britannica or to a commander in a successor fleet.” Alternatively, “a signet depicting a warship would have been a suitable device for a merchant who desired a talisman against piracy when on the high seas,” explains Alan. The intaglio is now in the Museum of London’s permanent collection.

Dolphin IntaglioSeveral years later another mudlark made a similar discovery. While searching for colorful glass beads along the Thames foreshore, Johnny Hines crouched down to look closer for the tiny, elusive objects. Out of the corner of his eye, he spotted a modern plastic crystal. As he reached to pick it up, an unusual oval-shaped object caught his attention. As he turned it over, he saw that a dolphin had been finely cut into a dark brown onyx stone in the nicolo style over 1,600 years ago!

As I was mudlarking near a medieval dock in Central London, I found a 700 year old brass seal matrix with an integral suspension loop on the reverse, which indicates that it would have been worn on a chain or leather cord around the neck. In the centre of the seal is the head of a stag, which was a common symbol in medieval times attributed to the Saint Hubert, the patron saint of hunters. Around the circumference of the round seal are the Latin words CREDE MICHI [MIHI] which mean “trust me.” The words were hand-carved in reverse so that, when pressed into melted wax, the letters are legible.

Inspired by historic Roman precedents, the Stuarts and Georgians in England created their own type of seal matrices in the 18th century using glass intaglios featuring natural and classical motifs such as mythological gods and creatures, busts of Roman rulers and English monarchs, etc. Although some 18th century intaglios are made of precious gemstones, craftsmen often used colored glass as an inexpensive alternative. According to Ward Oles, a researcher of 18th century material culture, the glass intaglios were made from soda lime glass, both vitreous and opaque. The glass was usually colored with mineral or metallic/oxide additives such as cobalt for blue, manganese for purple, etc.

Queen IntaglioA Scot named James Tassie created large quantities of glass intaglios in his workshop in London in the 18th century. He mass-produced intaglios by pressing repetitive designs into the molten glass before it hardened. This three-sided, “spinning” glass intaglio which David Hodgson found in the River Thames. Dating to AD 1707-1714, a bust of Queen Anne, her coat of arms and a crown surmounted by an orb and septres are illustrated on the different sides of the glass intaglio.

Royal IntaglioFor wealthy customers, James Tassie would carefully hand-carve custom-made designs into the surface of the glass. The vibrant, coloured glass intaglio (left) discovered by Florence Evans on the River Thames foreshore was hand-carved with interwoven cursive letters surmounted by a crown.

mudlark intaglioWhen mudlarking at night along the old docks in London, Mike Walker found a brass fob seal (below) with an exquisite glass intaglio. Based on the style of the seal, it is most likely from the late Georgian period. Set in a conical brass frame, the intaglio is made of dark green glass and is engraved with a highly detailed bust of a Classical figure. Mike explains, “A loop on the top would have attached the seal to a watch chain, probably alongside other items such as a watch winder and pipe tamper.”



Another fine example of a Georgian seal matrix (above) was found by Oliver Muranyi-Clark. A crown surmounted by a bull’s head is depicted on the flat surface of the Georgian intaglio made of green glass. Holding the carved glass in place, the circular setting is scalloped around the perimeter with a domed, eight-spoke openwork cartwheel shape which allows light to pass through the glass. A handle or attachment loop would have been fixed to the central aperture.

Seal MatrixOne of my own favorite finds is a highly decorated seal matrix from the 18th – 19th centuries. At the top of the rounded handle, the dotted outline of a heart is shown emerging from flowing flower petals. Below is a ribbed bezel surmounted by undulating flames. On the bottom of the seal matrix (below right), the cursive letters K and R are interwoven into an intricate, floral design which would have been pressed into the wax to seal an official document or letter.

Lost centuries ago in the River Thames, signet rings and seal matrices are wonderful personal items which reveal rare insights into the lives of Londoners and even Romans who lived in early settlement of Londinium. Although we have not yet been able to link these finds to specific individuals, the intaglios and seals are highly personalised to represent the status and wealth of the owner. Through the unique motifs carved into the various types of seals, we can understand more about the culture and customs of the times long ago. Next time you find a small, circular piece of glass on your local beach, double check to see if it’s a glass intaglio!

Mudlarking on the Thames Foreshore requires a permit. Learn about rules for mudlarking in London ›


View more of mudlark Jason Sandy's finds from London

Learn more about mudlarking


Learn more about the experiences of mudlarks, who search the shores of rivers, bays, and seas for historical finds and other objectsArticles ›

This article appeared in the Glassing Magazine September/October 2018 issue.

1 comment

Great item. Many thanks! Love you recent book Jason, which I am in the process of reading.

Susan Thurston June 06, 2021

Leave a comment

All comments are moderated before being published