If we could go back to the ale bottles for a moment... For comparison, here's a base that was excavated at Mt. Vernon a couple of years ago. It's 3 inches in diameter with a 1" dia. pontil.
Brian
Hi Brian, mine is just a hair over 3" wide but there is a flat rim about 3/8" wide around the outside of the base and is concave inside that. The glass is very thick. Yours looks to me like a larger utility/ink type cylinder.
It is probably the same style, different mold. I have shards from at least 3 diff sizes of ale/porter/min. waters with that flat base rim similar to the bottle I dug. Some are big like the 3pm quart John Clarke mineral water. I also have some that are tapered in from the rim without that flat part.
That is an extrememly thick base, and probably would have been an ale or porter. Funny, all of the examples that I have are with an early sand chip pontil or a later iron pontil. The only 3" bases that I could find with the same 1" tubular pontil were these utilities...