If you canned the tuna properly in a pressure canner for 100 minutes and the jar is sealed and you don't see any signs of spoilage it will be safe to eat.  It might not taste as fresh and the nutritive value might not be as high but it is safe.  A lot depends on where you stored it.  It will be quality not safety.  Go ahead and open it and you may want to use it in a casserole or add some additional seasoning.

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Nellie Oehler