In "What kind of lathe has V-flat ways rails with 80 degree V angle?" posted on 14 June 2013 to RCM, I asked if anybody could identify a steady rest with 80-degree included angle Vee-flat ways. I now have a photo and description posted on the metalworking dropbox. (The owner doesn't want the real URL published, to keep spam down.)
Google on Mystery_Steady_Rest.
The filenames are "Mystery_Steady_Rest.txt" and ~.jpg.