The hub pilot wheels use one nut to hold both wheels on. Budd wheels have an outer nut to hold the outside wheel on and the inner stud nut to hold the inside nut on. The Budds also had right hand and left hand threads. The stud nuts will have an L stamped into the end.
Definition(s) Flammable Gas. Substance that exists exclusively in the gaseous state at normal atmospheric pressure and temperature and is capable of igniting and burning when mixed with air (oxygen) in the proper proportion and subjected to a source of ignition.
It's not like everyone knew the derivation of the word, so the change probably made sense. However, confusion persists today regarding which word to use. Flammable is the modern term for a material that catches fire readily. Inflammable means the same thing. If a material won't burn easily, you could say it is not flammable or nonflammable.