With all the SB tags and legend plates I have played with over the years and also the time I spent at Tektronix in Beaverton Oregon were they had an extensive chem. mill facility. The older SB plates were or appeared to be chemically milled to create the raised detail. I say chem. mill rather than stamped because if they were stamped there would be impressions on the back side of the plate and I have never seen any on a SB plate.
Also at least the pre war data plates were not painted rather they were enameled. This was a process much like powder coating. The dry powder is applied to the recess areas of the plate and then they went through a baking process. That is what made them so durable. As this was done while the plate was dead flat after baking they went through a burnishing process to brighten the raised detail of the plate. I dont thing SB made any of there own tags and legend plats as there would have been companies that specialized in this area of manufacturing.
Dalton and Flather used the same company in Ma. to make there tags. The only difference in the two company's tags is the company name and address the tags are identical
Just like threading lead screws. SB never made any of there own except for the 405 left hand screw. All others were sourced from a sub contractor.
Some of the plates I see in the Amsted era are in fact just flat brass plates that have been silk screened. These did not hold up well.
