What makes a navy flake tobacco, “navy”?

Is it the addition of rum?
Is the the pressing of the tobacco?
Is it the blend?
I couldn’t figure it out, so I started researching.

Most are flavored with rum.
Most are aged under pressure.
Most are mainly virginia.
Some have cavendish, some have latakia, some have burley, some have perique.

I have not been able to determine if “true” navy flake should be a certain blend.

I’m trying to get together a decent sampling of navy flake tobaccos, so I can do a back to back to back (etc) comparison. I have a handful, and my next order will be as many other “navies” as I can find/afford.

Obviously, I’ll share my experience with the group!

Here's where I need your help:
Before I start this, do any of you more experienced smokers have more definitive info on navy blends?
What best exemplifies navy flake to you?
What is your favorite navy flake?
What are your “must try” navy flakes?

Thanks for your input!