This is a copy of a set of knuckles carried by "Bosun". This is what I found on the web.
This one was copied from a photo provided by the Maine Maritime Museum in Bath.
On the website, it was referred to as a set of "Boatswain's knuckles". I suspect that they simply belonged to a bo'sun rather than having any serious, nautical provenance.
Like the Royal Armouries knucks, they're large and roomy but are one-sided - index-finger must go in the index-finger hole, like the T-handle. Also it includes completely gratuitous knuckle points which take the form of blunted cones. Wicked.