Cheap, solid, small ish common battery.
How bad was it
Metering the grass outside through the french windows the reading went up about 2 stops when I got to the (open) window, it was due to flare from the sky. Proved by shading the lens with my hand.
Curing the flare
Simple, paint all the insides with flat black paint, I used Nextol Felt Black, mind you the inside is so shiny anything would be an improvement. You don't have to take the thing apart just unscrew the lens.
Metering the grass again, up by 1/2 stop with direct sunlight on the lens.