This allows you to re-cover the meter after removing the face plate, keeping dust and other air borne particles from getting into the meter mechanism. The next step requires a gentle hand. You need to remove the face plate from the meter housing. Unfortunately, the plates are glued to the plastic casing. If you attempt to pry the plate off, you will either bend the plate, or damage the very delicate needle mechanism of the meter.
Freeze spray makes it into an easy process.
Using a very light spray, freeze the metal plate causing the underlying glue to separate from the plastic. On these meters, there is a very distinctive cracking sound as the separation occurs. The meter plate will very literally fall out of the housing. With stubborn plates, a very light pry with your razor knife will supply extra motivation for it to slide off. Be carefull not to get any of the spray on your plastic meter bezel, as the chemicals in the freeze spray will cause a distortion in the plastic.