Jerry— This looks more like a modern made flask, possibly from the 50s or 60s, than one from “back in the day.” Or at least it does to me. My father made one sometime around 1962 or so that is very similar except for being cylindrical.
Yours is still very cool even if it is not an antique. Good find. Use it, I would—provided that it is air tight that is.
Hope this helps. —JB