I have had hundreds of IIs, IIIs and IVs go through my hands. 

The IIs & IIIs look identical on the outside. I have never seen a white II 
though. 

I always thought the 210s and 220s were IIs and the 225 was a III.

The real strange one was the IV. It had the Multibus card cage in a hump off 
the right side. These only came in white and had 5 !/4" drives under the 
monitor.

The original development system was the 800. It was a rectangular blue box 
that used a terminal to control it.

The 310 looked more like the traditional desktop box with 5 1/4" drives in 
the front and cards in the back. This was their regular computer system that 
used iRMX or Xenix as you indicated.

Then there were the 330s and the 380s which had a Multibus 1 cardcage and 8 
inch floppy and hard drives.  I have a couple of these still. Very heavy. 

The 3XX series were their regular computer systems, rather than development 
systems. 

Now what I had always wanted was one of the iPSC/1s. The only one of those 
Intel would let us have was a gutted case. It is pretty.
I may have some of the Multibus 2 Ethernet cards for those yet.