My 1930-vintage 20-gauge No. 4E with all the options is marked BEST FLUID STEEL and has the big D with a three-lobed crown over it that is the mark of Didiere barrel works of St Etienne, France. My 1936-vintage 12-gauge No. 4E skeet gun with all the options has the BEST FLUID STEEL marking but no visible tube makers mark on its very heavy barrels. My 1941-vintage No. 4E 16-gauge shows no markings on the bottom of the barrels.