[Ham-Mac] Slightly off topic, history of 850 Hz shift?

[Bob Nielsen]

I recall that hams also used 850 Hz shift when I first operated RTTY  
over 40 years ago, although 170 was starting to gain favor about that  
time.  The bands were less crowded then.  There were also wire- 
service (AP or UPI) transmissions just above the 20 meter band in  
those days, although you could go through a roll of paper pretty fast  
listening to them.

73 - Bob, N7XY