My tuna and egg sandwich thing started back in the mid-ninties in Kent, WA.
My big black good buddy Roger Cave told me the secret of tuna fish. I had always just bought chunk because it was cheap, but Roger had me try a can of solid white and I was amazed at the difference in quality and taste.
So I combined this tuna discovery with hard boiled egs, and started feeding myself, along with Riley and his high school buddies, this as a sandwich.
I was at a party with those guys when they were older, and they all remembered my sandwiches fondly.
These days I use Krogers Albacore Solid White Tuna, in water, wild caught, you get the drift...
As for eggs I use Krogers free range large. I only use one slice of sour-dough bread, fold it in half.