There are countless Dr Pepper sites. From what I've seen in the past 15 minutes of looking, your bottle may be one from the first years of production, circa 1885. The bottle you have does not display the 10 4 2 logo yet, and isn't shaped like the tall bottles of the 20s.
I saw something similar to yours on one of the sites that requested a thousand dollar donation for the bottle.
Narrow your search to vintage dr pepper to find a site that can authenticate it.
I've got a feeling its worth something...more than the original product, anyway.
What a cool treasure to find