My Luna Pro (Lunasix) ceased working yesterday when a camera store fitted new batteries

Completely dead, even with the old bateries again. I'm rather a long way from a repair shop, and need the meter.

However the fitting new batteries had to be a co-incidence as nothing untoward was done to the meter. Luckily re-examination show the needle isn't moving under any circumstances and the fault is now obvious, the glass screen has dropped and is fouling the needle, so it's a simple problem, open and re-position.

But how do I open up the meter ?