I was going to work on Große Grün yesterday, but the weather was that kind of threatening to rain in the morning that makes flea market vendors have conniptions about whether to go to work and get stuff soaked, or stay home and watch it mostly be a beautiful sunny day (because either will inevitably happen depending on what choice you make).
My initial project was... well actually, let me start by showing you the result:
That might not seem like an all day project, unless you realise that IBM never sold 100% Model Ms with more than 102 keys, let alone a Mac version. At which point, I will tell you that his particular keyboard is (mostly) a 1988ish 1391401, which is the NA English ANSI Model M that shipped with the PS/2. Yes, the ANSI one. No, that's not an ANSI layout; it is indeed, ISO.
If you know a lot about this stuff, this is not what it might first appear to be: a Unicomp Classic with an original Model M case on it, either.
The original project was to screw mod my 'worst' IBM 1391401 (I own 3). I had the idea of maybe doing this exact project at some point; in fact I initiated a request with Unicomp for the parts a few days ago. But when I finished cutting all the tendons (rivets) on the IBM, the barrel plate folded like a wet newspaper. It had quite a few bad cracks, and was not really reusable. So, since I don't actually like my New Model Ms, and because I have two of them so I can use one for reference, I decided I'd set about trying this experiment.
The "Mac" keys (control, option, command, 'Clear', '=' and single unit '+' key), the barrel plate, the six flippers under the upper nav keys, cable, membrane, and control card are off the New Model M. The '< >' key, single unit '\ |' key, and the ISO Enter key are off a Battleship I replaced the keys on. Everything else- the case, keys, flippers, and mounting plate are the 1391401.
The New Model M has a sort of harsh feel to it, I don't like it, after using real IBMs again for a while. I wanted to create a natively Mac compatible keyboard with a fully normal and intuitive Mac layout. Converting it to ISO was a last minute idea, honestly, and I'm not sure I'll keep it that way. Theoretically, all you need to do is plug its USB cable into a Mac and you're off to the races; it even has a function layer that will allow for standard mac Media and Hot keys.
Theoretically, because it doesn't actually work.

I didn't have the energy to resolve that yesterday, but I think it has to do with the connection between the membrane and the new-style Unicomp control card. Unlike every other Model M I have ever seen (including older Unicomps), this doesn't use a pair of ribbon edge connectors (one for the columns, one for the rows); it uses a single connector that gets folded over and the control card placed on top of it, and then screwed down. I have no idea exactly
how it does that, since you still have to have two membranes, one for columns, one for rows, that get pushed toegher, and a sheet to seperate them, so there needs to be two streams of data. I'm hoping I don't have to undo the screws to figure it out, but I may need to really take it apart again to figure out how the heck two separate membranes can be combined into one connector.
Fortunately, one of the advantages of screw mods is they are serviceable.