Maybe I didn't explain myself correctly.
If you try to find who the translator is and do not succeed, you can assume the translator is unknown. If the translator is unknown, the copyright expires 70 years after publication. If you are basing your text on a book published in 1922, the text is public domain (in life+70 countries) since 1993.
On the other hand, it seemed to me that
the translation you are interested in is the same as
the one I linked to (with maybe some spelling changes), and that one was done by White Kennett, who died in 1728, so, if it is indeed the same translation, it is in the public domain everywhere, regardless of when any edition was published). Have you found significant differences between both translations (ignoring the frontmatter)?
N.B. I know nothing about Erasmus translations, I just compared some random sentences of the two books, and they were the same.