It's all in the context.
OGR Forum: MR = Milwaukee Road
All the HO Forums: MR = Model Railroader
Psychology/Social Work: MR = Mental Retardation
Medicine/Physics: MR = Magnetic Resonance
Everywhere else: MR = Mister
That's the trouble with abbreviations. You guys had me going for about six months talking about ESE cars. I could not figure it out. Was it some modern subway car that I knew nothing about? Finally, one of you let it slip: Empire State Express!
Bob