Halibut for instance:How does it work?
Pack raw fillets into the cans until full, add salted water to the rim & bake in oven to specified temp for specified time, Use the machine to seal the lid (takes 20 very easy revolutions of the handle to seal a can), pressure cook @ specified temp & pressure. Flip them upside down & dunk them in water to see bubbles (bad). Bathe them in cool water & dry on a kitchen towel - sharpie a date on that puppy & throw it in the pantry.
Canned Tuna? pshhh - Meet canned halibutt, good luck keeping up.