A variant so archaic that I, a linguistic pedant par excellence, have never even once seen it used in anything written since the turn of the last century, save mentions of its existence as an archaic variant of the common form, and its usage in the phrase "weather gage", itself (and the concept it denotes) rather outdated since the close of the Age of Sail.
In any modern usage not deliberately aping archaism, 'gage' for 'gauge' is fairly called a misspelling.
In any modern usage not deliberately aping archaism, 'gage' for 'gauge' is fairly called a misspelling.