Atlas was a brand originally created through Goodyear so it's been around a long time. Your sign is one of several similar I've seen this year, most dating to 40's/50's The 'g' code is likely for style/shape of sign. Someone else can chime in on the mfg name as it escapes me right now. It's not a scarce or rare sign, but the contrast between red white and black is decent enough for many garage collectors to pick them up.
A fellow had a slightly nicer one two weeks ago at a swap meet for $275 and I had a much better one sell for $350.
