I have recently run across a number of references to the 1500s as being "T-54 class." I don't think I have ever seen such a designation on any Frisco reference unless it is supposed to be shorthand for Tonnage Class 54 (and weren't they Tonnage Class 56?). Did the Frisco ever use such a designation internally, or is it picked up from an assumption about the way the Frisco worked. I know many other RRs used such designations--the MoPac being an example near to home (e.g. BK-63 for their 63" driver Berkshires)--but I haven't run across such usage in or on anything Frisco.