This heavy-duty RTTY terminal unit was manufactured and distributed by Radio Wholesale in the 80's and early 90's. They are considered prize items when they turn up for sale. 

There were only about 300 units manufactured. Originally they were mounted in gray Ten-Tec cabinets, but because most of the ham radio RTTY stations used Drake twins as stations, several "special order" units were manufactured and mounted in Drake R-4C cabinets to match those stations. 

Mr. RTTY Terminal Units are noted for reliability and were used in many commercial RTTY circuits over the years