Mkemper,
I had the same question a few years back and could not find any photographs. Attached is a photo of the interior of the box I made on my customer's rifle. If I build another, I will use a tack configuration for the release. Mine worked well, but I still wonder how the original release, cavity, and spring looked like. If you find a photo of the original box, please send me a photo at rbpodge@twlakes.net. I have another rifle to build down the road a bit that will have a toe plate box. Good luck with the build.
Roger Sells