After 30+ years, most likely your original clock bezel has fallen apart, too brittle to be removed, or is completely gone.  Here's a modern take on a replacement: Multi Jet Fusion printed out of Nylon PA12, this replacement bezel is meant to last.  You can install it as is (original mounting hardware not included) or finish it however you desire.
 
*Price shown includes shipping to US Destinations. International customers please contact us for a proper shipping quote.