The real question is "What clef is this?". Any key signature with a single sharp is always G Major, but the line that the sharp is displayed on depends on the clef. The clef in the image is a Tenor clef, which is also called a "C cleff" because the staff line enclosed by the "arms" of the cleff is middle C.
Comments
It is G Major (or E Minor).
The real question is "What clef is this?". Any key signature with a single sharp is always G Major, but the line that the sharp is displayed on depends on the clef. The clef in the image is a Tenor clef, which is also called a "C cleff" because the staff line enclosed by the "arms" of the cleff is middle C.