surface gauge vs surface gage

surface gauge and surface gage both are nouns.

Word	Noun	Adjective	Verb	Adverb
surface gauge	Yes	No	No	No
surface gage	Yes	No	No	No

As nouns, surface gauge and surface gage are synonyms defined as:

surface gauge and surface gage: gauge consisting of a scriber mounted on an adjustable stand; used to test the accuracy of plane surfaces

Other synonyms of surface gauge include scribing block.

surface gauge (noun)	surface gage (noun)
gauge consisting of a scriber mounted on an adjustable stand; used to test the accuracy of plane surfaces	gauge consisting of a scriber mounted on an adjustable stand; used to test the accuracy of plane surfaces