There’s nothing different with these controllers internally. I’m pretty sure the compartment above the board is an external radio box. I’m not sure if Whelen still offers extra battery and external radio compartments. An example could be Tooele UT’s 2800s. To identify the three types Type one is simply the Vortex cabinet that doesn’t have an external battery compartment, Type II has a small external battery compartment, Type III cabinets have a larger external battery compartment (ESC-864 Type III enclosures would have two external battery compartment)
As far as I know, all of Vogtle’s 3000s had ESC-2020s on 435hz. I believe some of the ESC-2020 upgrades were FPUs? Surprisingly, they might have been the only WS/WPS-3000s running on 435hz ESC-2020 boards.
There’s recordings of them which are linked below.
https://youtu.be/_DFrbpiLr7g
https://youtu.be/VfVX4PlYXcQ