that jack [Denny's] was the standard until sometime in the 60's with very little change, - never heard the term 'piston jack', always called them screw jacks and the Chinese ones bottle jacks, a subset of hydraulic jacks
I notice in the pak Tim links, the bigger trucks "use tire changing iron" for the jack handle, that'd be the bottle jack I suspect, or you'd get some frustrated turning the screw with the screwdriver tip of a tire iron while hunched under a 2 ton
Bill
