Roswell Cook of Ilion, NY made this

[Wrenchmensch]

A nice carriage wrench with nut-retaining feature was made in 1885 by Roswell Cook in Ilion, NY.

[1930]

I cant see how the heck this thing works, does that arm pivot to hold the nut, it seems to me the two bottom pict. shows a different wrench, I can see where it might swivel on bottom pict. but cannot see the little rivet on the middle pict.

[Wrenchmensch]

One squeezes the little arm on the bottom upward against the main body of the wrench which pivots the nut-locking other end of the little arm inward into a shaft on the inner side of the square end. I believe the maker left a bar for the arm to pivot around in designing this wrench. This would eliminate the need for a pin. After inserting the arm piece into the wrench body, the maker then pinned the heavy spring to the top surface of the wrench.