Jamie,
I found a bottle just like this, and it still had it's original bakelite cap.
Mine as well appears to say Obo-Ro-no, though mine has a 5. on the bottom.
Like you I haven't been able to find much about this (yet) but I will say that this bottle came from a cache of bottles dug out of a riverbank dump site, the majority of the bottles coming from the 1920's the oldest one I found dating at 1934.
My guess is that it came from in between these times, especially since bakelite screw tops were used quite a bit in this time.
I know this post is rather old, but if you or anyone else has any more information on it since, I would LOVE to know. It is the ONLY bottle in my collection I have yet to identify as far as what it's contents were.