saturn model number

I am going to get a sega saturn and I was wondering if someone could tell me a way of identifying which model i would be buying? Also I will be putting a modchip in this so I need to know which model is better for the chip or are there any differences?
The first things to look for are round power and reset buttons. They indicate a Model 2, 21 pin Saturn. Unfortunately from there it's pretty much guess work as to which type of CD board you will get.

The only really 'bad' ones are the Sanyo CD boards with the 'PC trap'. Only one person has so far managed to mod one with the 'current' version of modboards. We're still not sure why.

If you get a Saturn with the 32 pin IC on the CD board, any 21 pin mod will do.

If you get a Saturn with the 64 pin IC on the CD board, my research has shown that only Gamegizmo mods will work with any degree of certainty. Some have had Lik-Sang/Lan-Kwei mods work, but most haven't.
Has anyone ever seen a model 1 with the LED's stuck to the top half of the casing and the door open switch also on the top half of the casing? I just bought one of these yesterday, and when I opened it up it really shocked me. I have never seen this design before. Anybody care to elaborate?
Isn't that just an ordinary Model 1 Saturn?
Well it's been a while since I've seen a model 1, but I don't remember having the door switch on the top casing. It was always a big switch that was stuck to the Main PCB on the bottom half of the casing. Also the PSU was not stuck to the top half.
Well, you've pretty much just listed the differences between a Model 1 and Model 2 Saturn.

Model 2's have everything attached to the base with the top being just the shell.
Really? My old model 1 had everything attached to the bottom casing. The LED's were also mounted directly above the controller ports on a different PCB.
There seem to be some Model 1/Model 2 hybrid Saturns as well. Basically a Model 2 21 pin Saturn (I'm guessing with a 64 pin IC) inside a Model 1 (oval button) casing.

These seem to be relatively uncommon.
Well I have owned 5 different saturns in the past, 3 model 1's and 2 model 2's. The model 1's were all 20 pins and they all had their "guts" on the bottom casing. This is the first time I have seen this perticular version of the Saturn. It might be a first production run, because the manufacture date on the bottom is April 1995. Anyways, I shouldn't be nitpicking because I got this Saturn brand new in the box for $40 with 4 games. The games were Daytona USA, NBA Action 98, Sonic 3D Blast and Panzer Dragoon all complete w/cases and instructions.
That's the first I've heard of 20 pin Saturns like you've described.

Thanks for clearing that up.