Usually the tube size is rated, hence the 1084 was a 14".
Go and measure your 17" CRT, you'll find a visable size of less than 17" - that's why a 15" TFT has nearly the same size as a 17" CRT. Stupid but standard.
My Sony 17sf has 15.75" and my ADI 5A 15.36" usable diagonal.
