I'd suggest using a slight bump map and adding it tothe glass and not making the glass totally transparant (just 99% transparant)

You'll probably need a reflection map for the galss and the pen (if you use a HDR image than you wont need to as it will pick it up in the render) Also some use of the fresnell effect mapped to the reflection value will make it look nice and a lot more realistic.

Personally I dont use the mental ray materials for things like plastic, metal etc, as I find it hard without the previews to get it looking like I want, so I would just use Blinn's, but thats just me.