These dirks would have been carried by Royal Navy as well as merchant marine officers, even, rather more rarely, by army officers. This classic dirk has a whalebone haft (which, at first glance, might appear to be of walrus ivory, but on closer inspection is definitely whale bone) and iron mounts. The style of hilt, pommel and grip dates it.

This is likely to have been made towards the end of the American Revolutionary War (Peace of Paris, 1783) or during the early part of the Napoleonic Wars (starting 1793). This would have been carried by an RN officer or HEIC naval officer, and this example is interesting in having a particularly long (approx 26") blade.