I am trying to trace the 'genealogy' of this work for my bibliography. In particular, exactly when it became known by this title and associated with the name of Eudoxos.
I have the following:
1688. Letter to the True Disciples of Hermes. by Alexandre Toussaint de Limojon, Sieur de Saint-Didier. On Adam's site at http://www.alchemywebsite.com/didier.html.
Looking at this, it seems to be the Six keys, with an additional 2 paragraphs at the beginning.
1723. A letter to the true disciples of Hermes, containing six principle keys of the secret philosophy.
This is in Didier's Hermetical triumph.
1740? Later edition of Hermetical triumph, but I don't have the text, or detailed list of contents.
1745? As above (actually the 1723 printing with a new title page)
1814. As above in Barrett's Lives of the alchemystical philosophers.
1850. The title now becomes 'The six keys of Eudoxus, opening into the most secret philosophy' and is in Atwood's Suggestive enquiry. Did Atwood re-title it?
From here on, this seems to be the version that is reprinted on many occasions.
"An English translation of Limojon de Saint Didier's 'Le triomphe hermétique'. which comprised Didier's French translation of a Latin version of the German work 'Uralter-Ritter-Krieg', with his commentary : this edition also includes an English translation of Uralter Ritter-Krieg, from the original German, i.e. 'The war of the knights'."
Are you sure there was a 1745 reprinting?
Reasonably priced copy of the 1699 edition here, with the notes referring to the first edition as 1689:
Thanks for that.
I have taken the information about the 1745 reprint from ESTC.
Imprint is: London : printed for Thomas Harris, [1745?]
I also have a note that says: The t.p. is a cancel; the work is actually that printed by P. Hanet in 1723 with Harris's t.p. added
I have not seen this copy.
The 1740 version has the imprint: London : printed by F. Noble, at Otway’s-Head, in St. Martin’s-Court, near Leicester-Fields, 
and an ESTC note: A reissue of the 1723 edition with a new titlepage.
The Leipzig 1680 version that Goodwill mentions is probably the Uralter Ritter-Krieg which appears in the Hermetical Triumph, but it does not seem (from Ferguson ii, 485) that the 'Six Keys' or 'Letter to the true disciples' is in this version. It is only 16 pages, so would not seem to have enough space.