From the AAR Interchange Rules. The term Grade is used to desginate steel strength, with Grade H being the strongest, followed repsectively by E and C. I'm not aware of any other grades or component classes. Note the System Special Instructions indicates tonnage ratings on Mountain Grade Territory different for Grade C and Grade E couplers, this is due to thier respective strengths.

Coupler type would be indicated by design, as in "Coupler, Tightlock, Grade H components required. Other applied considered Why Made Code: WR (Wrong Repair)" This from the AAR manual and is also found under UMLER guidlines for billing purposes.

Note that field vernacular, while ingrained, often does not comply with the dry language of a tech. manual. No one in my craft, regardless of seniority, calls these by Grade. They all call them by type, as I would too over the radio should the unfortunate need arise. Many people also call the corner step a Stirrup, but it's really a Sill Step. Stirrups are found on saddles. Sometimes the carknocker craft I left follows me around.