Pressure measurements/specifications are part of my daily work. I have never seen "b" referring to bar, also not in any of the many American (imperial) papers I

Pressure measurements/specifications are part of my daily work. I have never seen "b" referring to bar, also not in any of the many American (imperial) papers I have come across. So this is either properly old usage indeed, or very specific to certain regions or industries (like usage of relative v absolute pressure). Or Wikipedia being properly pedantic.