The embossing is too vague in my opinion (save the writing). I believe the real flasks have more detailed imprints, even if they are faint. Who knows, though. Someone else could give you a better opinion.
I'm guessing repro. To me it looks very similar to Success to the RR flask that I've seen that are repros. It has that fat look. I believe most flask like that were a bit flatter to make them easier to pocket. I'm probably wrong though so don't listen to me. Swiz
It is a repro. The 1st ones were made in the 1930's...maker unknown. Later ones were made by Clevenger Bros Glass Works of Clayton NJ. The best way to tell an original of this flask (GI-28) is, the embossing is much more distinct and the letters have serifs...