Giannozzo Manetti (1396-1459) was one of the intellectual giants of the 15th century in the field of translation. His translation of the New Testament remains (as far as I can tell) unpublished. However, thanks to the digital age (and thanks to James Snapp pointing my way to the manuscripts), the manuscripts are available to view online. At Revelation 16:5, Manetti has:
et audiui angelum quartum dicentem. Justus es domine qui es et qui eras Sanctus. quiaa hec iudicaste.
The Greek from which Manetti was translating is known. The Greek manuscript he used for Revelation 16:5 is this:
As you can see, the text here is: … ὁ ὢν καὶ ὁ ἦν ὁ ὅσιος …
Evidently, Manetti also had access to and relied upon a Vulgate manuscript:
It is interesting how the “fourth angel” and “Lord” crept into Manetti’s “translation” of the text here.