Yeah, lack of a real definition doesn't help. But referring to the photos in this thread where others have compared this jacket to doublets that have collars and are meant to close (if even only at the top), this jacket just doesn't seem to be in the same category. I always see doublets in the Highland style having a rather military look to them, but this one looks more like a classic Highland civilian jacket... but with no visible collar and the interesting lapel style, amongst other unique parts.