I think you nailed it.This must be a 1st run Z-750Originally Posted by Überstationmeister:
I have never seen such a sticker but it might be indicating that the "wave" produced is not a pure sine wave and may cause some trains (even early MTH ps1) difficulty. This was a serious issue briefly in the mid 1990's and led to the marketing of "pure sine" transformers. I have an early MTH ps1 northern that refuses to leave neutral when used with my z-750 but this is the exception, not the norm.