Over the last two decades, Hans Eberhard Mayer has rendered tremendous service to historians of the crusader states of the Middle Ages. In addition to a history of the chancellery of the kingdom of Jerusalem, published in 1996, he oversaw in 2010 a monumental four-volume collection of the charters known to have been produced in the kingdom. The volume under review, prepared in collaboration with the Byzantinist Claudia Sode, serves as something of a companion to that much larger project. It contains descriptions of 111 seals, with illustrations where possible. Nine of the seals were struck for queens, two for a bailiff and one for a bishop. The actual survival record, however, is much thinner than those numbers suggests. Thirty-seven of the seals have been lost. For their descriptions Mayer and Sode rely on earlier accounts, some dating back to the Middle Ages. Nineteen of the illustrations are sketches of seals whose originals have been lost. Others are reproductions in wax or metal of the original lead versions. Indeed, the longest section of the introduction (pp. 35–57) is devoted to nine seals (groups of two and seven) that Mayer and Sode demonstrate to be forgeries made possibly in Constantinople in the nineteenth century, created to accommodate what was apparently a booming market in medieval antiquities. Forgeries though they may be, the authors ultimately conclude that they were based on actual seals that have since disappeared. Given the number of problematic, lost or missing entries, this volume reminds us just how much physical and literary evidence from the Latin Kingdom has been lost. What most usefully emerges here is a sense of continuity in the diplomatic practices of the Latin Kingdom. Baldwin i (r. 1100–18) established a basic design for the seal – round, made of lead, with an enthroned king on the obverse and the city of Jerusalem on the reverse – that his successors followed with only slight modification until 1225. Beginning in that year, when Frederick ii obtained the crown of Jerusalem through marriage, the kings were foreigners whose primary political and territorial interests lay outside the kingdom, and their seals reflected these outside influences. Wax seals also became common at that point, along with occasional golden seals. Some of Mayer and Sode's conclusions seem uncertain. Baldwin i, for example, is said to have used five different seals over the course of his reign. The evidence for one of them, however, rests on a single modern sketch, and two of them derive from the above-mentioned forgeries. There is also relatively little historical context or interpretation of the seals' iconography. On the whole, however, the book is a virtuoso demonstration of a historical art to which many medievalists will have had only passing exposure and a remarkable piece of scholarship, service and detective work for which all students of the crusades will be enormously grateful.