I have a couple of meters with analog scales and want to know why they have a shiny metallic area following the scale.
The mirrored bands are to solve the problem of parallax when reading the meter. The technique for reading the meter is to adjust your head position relative to the meter so that the reflection of the pointer is obscured by the pointer. Then you are confident that you are looking at right angle to the scale and can read the value without parallax error.
Figure 1. Needle reflection is visible and reading appears to be < 0.4.
Figure 2. Needle reflection is obscured by the needle itself and reading now appears to be much closer to 0.4.
Images from YouTube.
When the reflection of the needle disappears behind the needle itself, the reading is accurate. Otherwise, you may be looking at an angle, and reading the wrong figure off the scale.
(Presumably on the SWR power meter, the reflected power is either less critical, or known with less certainty, so it doesn't need parallax control. Typically you'll tune something for minimum reflected power, and you can see the needle reach a minimum from any angle)