The permissible flashlight was designed to be used in special environments.
"Permissible Electric Flashlight Approved for Use in Methane and Air Mixtures Only, DEPARTMENT OF THE INTERIOR BUREAU OF MINES, Approval 618 IISUED TO THE FULTON MFG CORP WAUSEON, OHIO"
"FOR USE IN THE FOLLOWING EXPLOSIVE ATMOSPHERE ONLY. GASOLINE, PETROLEUM, NAPHTHA, ALCOHOL, ACETONE, LACQUER, SOLVENT VAPORS AND NATURAL GAS"
These items were left by the Americans in Vietnam after the war.