It's nowhere near as widely used, but there is such a thing as a 2.5mm jack, and you can buy a converter from 2.5mm male to 3.5mm female. Has any telephone handset ever had a 2.5mm headphone jack?
(Presumably no telephone handset has ever had a ¼-inch jack, even in olden times?)
(Presumably no telephone handset has ever had a ¼-inch jack, even in olden times?)