Possible Naval Dirk
 

I also picked this one up as well.

Interesting hilt.

12 inches overall. 7.5 inch blade.

A couple of additional images

You appear to have a notable interest in naval dirks, and not surprising as these have a colorful history of their own as unique weapons which were often used as required and outside the normal parameters of weapons more standard.

The weaponry aboard naval vessels were of course more regulated, but in the multitudes of private vessels, merchant or other, weapons were purchased by the captains through private purchase. As these were not in accord with any regulation, they might have been surplus or otherwise types in variation.

The dirk, and knives in that category were sort of between a knife and short sword, and it seems private sailors often took it upon themselves to have examples of 'one off' versions, as this appears to be, crafted. It seems this kind of repurposing is rampant in all sorts of weapon forms, and ethnic or national contexts.

This interesting example appears one such case with some sort of perhaps furniture element for hilt and cut down blade, possibly a bayonet.
It seems the blade length would be short for a dirk though, in my experience these were usually 12" or more.