Though myself and others have found natural dark SCA bottles I'd bet that one was nuked. You can usually get them for cheap because most knowledgable bottle collectors don't like the effect. If ya really like it though, buy it.
Definitely looks too dark ,sometimes noncollector people will buy for more than it is worth because they like it .Here is picture of one that has been subjected to some type of rays (x-ray or gamma rays ? ) with a natural sca beside it .
Hi Don. Like one of the previous posts states that Chero Cola bottle has been nuked. By nuked I mean someone put that bottle under either an x-ray machine, meat sterilization machine, or exposed it to a very strong UV light. Your bottle was originally aqua or clear. When it was exposed to those high doses of the rays the chemicals (more than likely maganese) in the bottle reacted and a color change occured. You see this alot in the early Chero bottles.