Go get the 10oz Oyster Jars at Brady's Oysters in Westport; case of 48 is $22.50 NO lids. They are regular mouth jars with straight sides and are PERFECT size for canning tuna. 26 jars fit in a 23qt Presto Canner.
8 nice Albies turned out 48-10oz, 24-WM pints Saturday and 8 nice vacuum sealed top loins. I used Serrano's, Jalapeno's, Lemon Pepper and Sriracha in different jars making sure to dry (after tightening) and sharpie the lids so you know what you have inside.
My Ball Blue Book says 1/2 teaspoon salt in 1/2 pints and 1 teaspoon in pints. I put the salt in the bottom of the jars and it turns out fine every time with no complaints from anyone.
I had 1 of the 10oz jars (with serrano) not seal which was all good...made tasty sandwiches for my daughter and I.
On how jarred tuna tastes over time; I had 2 jars from 2012 that I finished off a few weeks ago that tasted fine, probably 2dozen jars from 2013 left and they are fine. Fresh canned -vs- older...to me there is no difference in flavor/quality. I guess if you keep it cool and dark, it should last a long time.