Mike — My first thought, with that complicated shape at the other end, was a bell clapper. Probably, as Frank suggested, part of an apprentice march frigger. Don't assume that this giant bell wasn't functional, as, after reading in Strange & Rare
about a 9" glass cannon (another apprentice march frigger) that had signs of actually being fired, anything is possible.
Full length glass clappers are known — Walsh bell clappers are like this. See Reynolds fig.43.
There must have been prizes awarded for the best of these apprentice march friggers, so somewhere there must be records of these prizes. I wonder if there's an article on this in one of the glass journals. Does anyone know?