Telling Allison Transmissions apart

what is the easiest way to figure out what transmission a truck has when an inspector is asking? how can you tell the difference between an Allison 2000, to a 3000 ETC? Or where are places on most trucks that it might list that out?

 

What is the easiest way to figure out what model transmission is in a truck at any time? I know that sometimes it will list out the transmission model for Allison. With Eaton Fuller, you can look at the shift diagram to figure out what model it has. With Allison there is that same shifter plate. I'm asking how to tell which model Allison it is (without crawling underneath to look for serial numbers)