Joe, the bubble type bottom on this bottle is completely uniform in curvature. There are no indents from coals or fire, and you would think that the bubbling would have been into the bottle and not out. However, that is a good idea and may be a possibility. Its very odd.
Thanks for coming up and digging with me by the way. Its always nice to have some people to joke around with while your digging. Plus all of those magazines and books from you and Fred will keep me busy reading and out of trouble!
There are some round bottomed inks that were intended to fit in school desk slots or in desk set slots. That bottle is pretty big to be one of those though. I wonder if it was a filler intended to fit in some sort of machine that printed?