@gunrunnerjohn: the tender shell appears to have locations for two switches and a volume pot.
I'm in the process of trying to map everything out, but thought I'd share the attached photo.
I'm thinking red is volume pot. Green is smoke switch (says so on top of the shell with cast-in lettering saying "smoke unit on/offc)
Orange=??
Orange has cast-in standoffs so the switch that fits there would be deeper / larger.
The tender appears to have two holes in the back for backup lights. Maybe something to do with that?