One of a group of specimens illustrating copper smelting - a sample of copper containing sulphur and other gaseous matter, which when fused and setting escapes and throws up metal forming a volcano

Red sulphur cast of the reverse of the Great Seal of William I (of Scotland), depicting the king as a knight on horseback, c. 1165

Red sulphur cast of the obverse of the Great Seal of Alexander II, depicting the king on his throne, c. 1214

Brown sulphur cast of the reverse of the Great Seal of Alexander III, depicting the king as a knight on horseback, c. 1249

Red sulphur cast of the obverse of the 2nd Great Seal of Alexander III, depicting the king on his throne, c. 1265

Brown sulphur cast of the reverse of the 2nd Great Seal of Alexander III, depicting the king as a knight on horseback, c. 1265

Brown sulphur cast of the obverse of the 1st Great Seal of John I (Balliol), depicting the king on his throne, c. 1292

Brown sulphur cast of the reverse of the 1st Great Seal of John I (Balliol), depicting the king as a knight on horseback, c. 1292

Seal impression in red sulphur, of the reverse of the 1st Great Seal of Robert 1 (Bruce) of Scotland, depicting the king as a knight on horseback, c. 1306

Brown sulphur cast of the reverse of the Great Seal of David II, depicting the king as a knight on horseback, 1329

Seal impression in brown sulphur, of the reverse of the Great Seal of Robert II of Scotland, depicting the king as a knight on horseback, c. 1371

Red sulphur cast of the obverse of the 1st Great Seal of Mary, Queen of Scots, depicting the Queen on her throne, c. 1542

Red sulphur cast of the reverse of the 1st Great Seal of Mary, Queen of Scots, depicting the royal arms, c. 1542

Red sulphur cast of the obverse of the 4th Great Seal of Mary, Queen of Scots, depicting the King and Queen on their thrones, c. 1559

Brown sulphur cast of the obverse of the 7th Great Seal of Mary, Queen of Scots, depicting the Queen on her throne, c. 1564

Brown sulphur cast of the obverse of the Cokete Seal of Dunfermline, depicting St Margaret between shields bearing the royal arms and the arms of Dunfermline, c. 1312