Can anyone provide me a beginning date for when manufacturers of
bottles, jars, porcelain insulators, etc. started putting "REG. U.S.
PAT. OFF." (no patent date included) on their products? I've reviewed
standard references for glass and ceramics and found no mention of this
mark, although one web page states it dates to circa 1932, which seems
too late to me.
 
Any assistance will be greatly appreciated.
 
Michael M. Gregory
Great Lakes Archaeological Research Center
Milwaukee, Wisconsin
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