I don't know much about suspensions but thought this was of interest. I had noticed that all suspensions produced in North America that had markings on the metal caps were incised. On the other hand all European produced suspensions were embossed.
These three discs are all Ohio Brass 6 inch porcelain.
The first disc has incised markings except for the 1960 which is embossed.
The second disc, produced a year later, has all incised markings, is typical of most NA production.
The third disc stamped '8 OB 8' on the porcelain, has a cap that is 100% embossed.
If anybody has comments, I'd be pleased to add the information.
Bud Johnson adds....I have suspensions made in Mexico (HECHO EN MEXICO) that have embossed markings ..