Got RUST? It's easy to remove, here's how.

[Patrick Chadwick]

OK, I admit my ignorance. What is naval jelly?
I deduce from the correspondence that it is not a kind of food served up on board warships.

In the previous post it looks as if the upper(jellied?) half has been slightly etched to create a matt finish.
The lower (Birchwood Casey) half has preserved a better surface.