I found these specs for that monitor, but as PBHarris said, it appears a Silicon Graphics, not Sony.
Of course, now I notice it says Sony Trinitron OEM....
Silicon Graphics GDM-17E21 (Sony Trinitron OEM)
Resolution: H Max = 1280 dots, V Max = 1024 lines
Deflection freq: H = 30-85 Hz, V = 48 to 150 Hz
SGI Part No.: 061-0010-001
Vertical Scan: 48-160 Hz
Horizontal Scan: 30-85kHz
You might want to open your /etc/X11/xorg.conf file and make sure those are the values entered for your monitor.