we will need to see the mark to further research this. There are so many G marks in so many variations. Also any related history would be great.
If it was made in the US, which is most likely, you might like to research the mark by going to Jewelry Resources and clicking on the link US Jewelry Marks 1922 - From the Jeweler's Index 1922 edition.
US maker's are listed alphabetically. There is G within a diamond in the G section in the Index.