Something completely new to me

[Shell Shifter]

Take a gander.
Length: 4.9in (124mm)
Thread OD: 2.7in (67mm)

The metal part is magnetic. The tip is white porcelain. I suspect that it screws on but is immovable.

At first I thought that it was a fantasy piece made by a collector but the porcelain fits perfectly so I seems to me to be purpose built.

Thoughts?

 

[HAZORD]

Proximity fuze body for older style U.S. Navy projectiles, 5 inch, 6 inch, 8 inch, 16 inch.

 

[Shell Shifter]

Proximity fuze body for older style U.S. Navy projectiles, 5 inch, 6 inch, 8 inch, 16 inch.

Thank you.