The so-called "sword" of Plougrescant (Côtes d'Armor, France) was found in 1845 by a farmer in a field belonging to a late advisor of the Royal Court of Rennes, Mr. Cavan. It would have been discovered close to four socketed axes (one of them is now in the museum of St Brieuc) although this association is highly unlikely. The sword passed through many hands before being purchased in 1867 by Mr. Gaultier du Mottay, Breton correspondent of the French Commission topographique des Gaules for the benefit of the archaeological museum of Saint-Germain-en-Laye, where it was registered under the number 7600. It is the oldest and the first of the six very similar "ceremonial dirks" known in Western Europe that has been exhibited in a museum. The circumstances of its discovery are unfortunately largely unknown. It is not as preserved as the others: the tang is slightly damaged and the corrosion has largely extended, except on the central part which remains smooth. The presentation of this sword will be an opportunity to ask questions about the making and the goals of this sword: How was it casted? Was it a finished object? How was it used or displayed? We will also discuss the production context of this object, which shows some parallels with the Tréboul-Saint-Brandan swords, typical of the Middle Bronze Age in the northern Armorican peninsula, which can be considered as functional equivalents of Ommerschans-Plougrescant dirks.