[Lee]

Continuing to ponder...

Unfortunately, the "belly" of the this blade is in the wrong place compared with Dr. Hoffmeyer's examples, which are also relatively wider, as may be noted in the superimposed image below.

I agree with Matchlock's impression of the tang button, I have exactly the same gestalt. This full tang with retaining button points either to something early (and possibly related to the knife daggers illustrated above) or something much more recent (18th century?). Considering the find place and the appearance of the corrosive attack upon the metal, I favor the late Roman attribution over a worn down peasant's working knife, but then, I am a romantic.

Though I continue to peruse, I fear that my library will fail to provide more examples, but that is the remaining task, to find if the Hispano-Roman form also includes examples from a known context with the "belly" more towards the tip...