Seems the early RCA TM-10 (15") and TM-21 (21") round screen color monitors come as close to over- built military specs. as any roundie. Rack mounted and used in both studio control rooms as well as remote broadcast trucks. both built like a bank vault, and weighed almost as much. 21" pictured here:
http://www.earlytelevision.org/images/RCA-TM21D.jpg
Courtesy ETF site from the John Folsom collection.
-Steve D.