From the seller...
"know right, this pipe has something about it that is catchy to the eye. When I saw it, I bought it immediately. There is no true specific dating data for GBD pipes but there are some signs that this may be pre-1950's. From everything I read GBD has always offered an insane amount of different models/shapes. However, a couple things to note. First, the bit isn't marked, could it be a replacement bit, maybe but I believe it to be original. It is not marked of which started happening at a later date, I believe in the 50's or 60's. Second, the "hoof" built into the bottom of the bowl. This hoof design was the standard from the late 1800's up until the 1950's area. In that time frame almost all GBD pipes had this hoof design such that there pipes could be sitters. I read that this went design feature went out in the 1950's. Also, I looked at as many pipe shape charts as I could find (mostly post 1950's) and could not find this pipe shape or the "Plain" line. So in short, purely based on speculation I would say pre 1950's I'm just not sure any further than that."