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.
This material is an EXTREMELY FLAMMABLE GAS. (It can also be a COMPRESSED GAS.) It is VERY TOXIC INHALATION HAZARD and an EYE IRRITANT. This material is also a significant confined space hazard (toxicity, flammability, explosion). Liquefied hydrogen sulfide escaping from a cylinder can cause frostbite.