Now that I have the IBM Model M, it's time to strip it down ready to adjust the keycaps, take some measurements for the brass side pieces and to size it up for the brass channel I'll need to mount it in.
First up then is to remove the four screws underneath at the rear of the case, in order to release the gubbins inside. The four screws can be seen in the pic below - note that three of them are inset and one isn't. The screwheads are 7/32" A/F, for which I used a socket.

The body of the socket was too big to reach inside the screw recesses, so a bit of (very careful) judicious grinding took place to reduce the diameter of the socket to just under 1/2" diameter (12.7mm) to fit the recess and reach the screw head. The ground socket is below - if you have a deep socket, that'll probably be the right tool for the job and fit admirably! (The pic is blurred - it's not your eyes!)

From there, with the screws removed, the bottom should lift away to reveal the metal plate below. The daughterboard is held in place on the bottom plastic plate, so be careful when lifting it off. The scket that holds the daughterboard will slide out, leaving you with the exposed underneath as below. Be careful of the strips with the conductors in! If you damage those, the keyboard won't work and the same goes for the daughterboard - handle with care!

So, with the main keyboard bit lifted out....

The plastic bits can be reassembled (to keep the screws from being lost!) and put in a "safe place". I don't think we'll need the plastic case again, but I'll keep it for nostalgia!

So this is what we're left with at the front...

And the back...

And the side view...

The next job is to remove all of the keycaps..sometimes, when pulling off the keys, the keycap won't separate. Just remove it gently....

...and put it back on for the moment.

The wide keys (like the Enter Key, the Ctrl keys, backspace etc) don't have removable caps like the smaller keys. Don't discard them though, as we'll need to reuse these too.

So, remove all of the keycaps and put them somewhere - I stored mine in a plastic yoghurt pot! We won't need these again either, but again, kept for nostalgia! To remove the keycaps, I either used my fingers, or for the qwerty keys that I couldn't get my fingers in to, I used a wide flat-blade screwdriver and gently prised them off. The less damage the better, although the keys need to be changed later (in order to stick on the typewriter keys) it's good practice to do as little damage as possible!

Once all of the keycaps have been stripped, the board looks like this below. Note the spaces....

Which is where the wide keys were...

And here....

And here.

OK, so that's the keyboard almost stripped and ready for action! I've kept the keycaps on for the moment, as (as can be seen from the pic above) there are some small springs in there (the switch actuator springs) that could get lost.
The actuator PCB can (very gently) be "unplugged" from the rest of the keyboard by gently pulling the plastic transparent strips from the plugs on the board and the three status lights plug. Put the PCB in a safe place (!) and be very careful not to damage the connector strips as it will render the keyboard useless!
The next task is to create something to trim the keys to make the typewriter keys sit nicely and to design the side supports (the brass plate).