My daughter has this exact same bottle. She loves hers because E. R. O. are her initials. I have no idea where it's from or what the initials originally meant, though.
I did a quick search. In terms of bottles, it comes up as an ear-drop brand. That's all I have. This one is much more modern, and has a dropper: https://img0.etsystatic.com/000/0/5757628/il_570xN.251498560.jpg Yours is much older, and might not be related at all. Who knows.
Are those guns you found in the immediate background of the bottle? Exactly as I'd found mine.
I have to go with 2find on this for sure. Depending on the glasshouse and country of origin, 1920 could be an easy fit for date. It also looks like a non US bottle, likely Britain.