Lost resolution setting following upgrade to El Capitan

Hi,

I have lost the option to select the native resolution display (1680 x 1050) in the display pane following my upgrade to OS X El Capitan. The external monitor I'm using is a 22LG3000. Is there any way to get this option back? I have tried pressing the option key to display the additional resolutions in the Display pane but this one is not listed.

Thanks, Hardev