HarvestReaper - you forgot the AFDS system complete with an additional 4 firing switches (float switches), which I presume is fitted to all N Sea 332Ls these days (should be, anyway).
Pilot's inflation button is recessed into a side-facing pod under each collective, plus one on the centre console. AP disconnect (not that anyone would be likely to want to disconnect the AP in flight) is on the cyclic.
I'd put my money on the AFDS, but since the AFDS cannot fire the floats unless they are armed, and since they shouldn't be armed above max speed for arming/inflating, an inadvertant inflation is nothing more than an embarassment.
HC