Originally posted by Bengan That is the (+) contact. Battery should be inserted (+) down. (-) is the housing.
The wires are not connected under the round plate.
I don't think the round plate is relevant. This appears to be the bottom mount for the take up spool part of the film transport.
In the first of your two most recent photos there is, immediately to the right of the central tripod mount, a sprung contact with a black wire connected to the bent up solder tag. This would appear to be the inner contact of the battery compartment. The baseplate appears to be missing the relevant hole, and the screw cap to hold the battery in place. I am not aware of the details of the construction, as others will be, but I'm not sure you are looking at the correct component. If you look back through the photos, the battery compartment in the baseplate is close to the tripod mount - the black plate is not.
Colin