A bit of history
The original Northills were made by the Northrup Aircraft factory for the PBY seaplanes.
They were made out stainless steel
sheet metal and could be dis-assemble for storage
in the nose of the aircraft. They were made out of stainless so that they would not effect the aircraft's steering compass
Each of the original Northills had a serial
number on it as each anchor was specific to a particular aircraft.
And now you know