Dash dimmer trouble?!

Do any of you know how to remove the dimmer knob from the front of the tach? Something is wrong with my dimmer and I have to take the knob off first in order to remove it from the back. So far I've got conflicting answers, one saying to just pull it off and another saying to unscrew it counterclockwise. I've tried both applying reasonable force to no avail. I'm afraid to apply very much more force for rear of breaking something until I know for sure what I'm doing. In case it matters, this is a '96 355 Spider. Can someone help me?

 

Great! Thanks Watson. A picture is worth a thousand words.