My Gossen Spot master broke down a year ago and I decided to try to fix it myself. Like Ian I found no obvious way to disassemble the meter. Apparently Gossen likes to hide the screws that hold the meter together behind plastic plugs. Looking at my Luna Six I’m guessing that the screw heads are located under the three grey plastic plugs at the bottom of the meter.

Hopefully someone who has some actual information will chime in…