Steuben used a Fleur de Lis acid stamp as one of their marking methods, and the forgeries of the stamp are rampant. They also used an acid stamp block letters, and you had best know the glass, or really know how to tell the bad stamp forgeries...
Acid stamps actually make it easier to mass produced forged pieces once you cut a stamp, and today that is pretty easy.... Make the mark in a program and provide a pdf to your favorite stamp maker like Office Max or Office Depot....
Actually, I bet the Dremmel owners wish that more acid stamps were used.... then they would not have to work on their Dremmel penmanship so hard...

Craig