Historical prices need a declared comparison method

How should a naval historian convert historical prices into current money?

Print the original price and add a clearly qualified modern comparison in a footnote, because no conversion factor is fully satisfactory.

Historical money does not translate cleanly through a single universal multiplier. The original figure should remain in the main text so the source value stays visible. A footnote can then supply a modern comparison and name the metric used to calculate it. Readers gain a sense of scale without mistaking the result for a perfect equivalence.