Speedometer glass and face cleaning

[bkksl]

I am trying to clean the inside of speedometer, its quite foggy. I have already removed speedometer from the dashboard and remove the rubber cover however can not find ways to remove the glass and get to the dial face. An advise on how to disassemble speedometer and refurbished them is greatly appreciate. 

[Cees Klumper]

I pried off the chrome ring on the front that holds the glass to the instrument with a small screwdriver. Cleaned the glass, then crimped the chrome ring back on, carefully. You can't see from the front that the chrome ring has been off (from the back you can see it, but you never see the back).
There are also businesses that do this more professionally, with new chrome rings, but in my case my solution worked just fine.