Yeah but many a product was found to be dangerous long after they were put into common use. I think it's like the posh California hotels with a brass plaque saying there are chemicals inside that the state of CA says cause cancer. Pretty small risk, but don't give 'em to kids.
OK, you peaked my curiosity, had to look up the history. The first lamp was 1905, but the first one I saw with the types mantle we're familiar with was around 1950, so you were right.
