I think it would be best to try to match whatever was on it to begin with. If it looks like it was oiled, then I would probably go with BLO. If it looked like it finished with shellac, go with that. I’m not sure that the whole oil immersion camp can make a case for longevity vs. any other finishing method.
Thus, go with conservation. If it’s old, keep it as close to original as possible while maintaining usability and period correctness. Unless you just don’t care about conservation – then finish it however you like!
The short version of the above is “It doesn’t matter – pick what you like.”
That’s my two cents. Many, I’m sure, will disagree. Hopefully they’ll come here and respond!