What was the purpose of the leather stock worn by Marines historically?

The leather stock worn by Marines historically was primarily designed to protect against saber slashes. This piece of military equipment served as a protective collar that covered the neck area, offering some defense in combat scenarios, particularly during the 18th and 19th centuries when close-quarters combat with sabers was common. The stiff leather construction helped to deflect blows and offered some rigidity, improving the wearer's safety in battle.

While other options like displaying rank, serving as a uniform identifier, or signifying training may have had relevance in military dress and decoration, the primary function of the leather stock was protective in nature during a time when saber duels were a significant part of military engagements.