Hi, I don't think they formed until after prohibition but I could be wrong. Most nips (and that's what it sounds like) were post prohibition with the start of commercial air travel. I'm not saying there wasn't any prior but... .I need more information.
1930s/40s is pretty spot on. Continental made a lot of different brands and spirits. If it was a gin, it could be Cavalier. without a label, it is has minimal value. while airlines are where most of us got first exposure, minis from the rail road lines are goodies. Old Forester is one brand to look for.
Yup, that's the back if the other side is blank for the label. Definitely after 1900 but I'm not sure if the nips were required to carry the "Federal law forbids....." mark. If it was to travel into international flight it may not have anyway. I'm not sure of those laws.