1.) Bring a torchlight (bright white light) to check for FUNGUS and dust when open the aperture blade.
2.) Smooth mechanical function of the aperture blade (open and close smoothly), no grease marks/leakages
3.) Check focus ring, smooth when turning or not.
4.) Yeah, front and back elements coating (got scratch or not)
5.) Focusing mechanism (sound, accuracy)
6.) Check images from shots (check for backfocusing, observe can focus accurately on the subject that you point with focus point, increase/decrease aperture to check bokeh/ depth of field)
7.) Check exterior (any dented part around metal mounting and lens body, metal connector pins etc)
8.) Request purchasing receipt and most importantly warranty card (looks like a nikon paper with serial code)
Don't hesitate anymore, good deals wait for no man...if you are okay with topping up RM50 for a better gold wording (which is more presentable, at lease can know owner has taken good care of it)
Sharing some experience from newbie. Cheers

and it seems like the wording not so bad after all.. the gold wording pic below