Then a pipe wrench after it's moved a bit.Hammer and a punch will do it...
SR
Yep, the right tool for the job,I suspect that since 1920 the most commonly used method or loosening and tightening was a hammer and drift as Sawyer Rob suggested. An adjustable (or appropriately sized fixed) "C-hook spanner" e.g. Proto #JC472, JC479 or similar may also work, and you can spend as much on quality as your wallet will stand.
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