I seem to remember that the glottal stop was represented by an upside-down question mark in Phonetic Script, but I may be wrong; it was a long time ago that I 'did' Phonetics as a module.

It's interesting, isn't it, to see various forms of punctuation used in an attempt to represent accents. One could easily just write, "Ow's Arry?" But the ubiquitous apostrophe makes it "'Ow's 'Arry?" Cockney, like Lowland Scots, is choc full of blessed apostrophes.