This is a tach, which I had to replace the glass on.  Note that the tach and the speedo are essentially the same instrument, with the addition of the odometer worm drive and mechanism.   I took the time to strip, clean and lube before replacing the bezel.  I am going to try a few different ways of attaching the bezel with this, to avoid the beat up look from prying them off and hammering them back on.

General: This is generally better built than the earlier model.  The castings are better, and the instrument is much cleaner, probably because the Commando mounts include dust boots to keep all that crap out. There are some improvements, the spindle plate and odometer axle are held in with a fairly hefty retainer, replacing the expanding plastic rivets.  This should make the instrument smoother, as vibration here would cause a fluttering of the needle when the distance between the aluminum disc and the magnet rotor varies.  There is also a plate added to retain the rotor.  Since failures seem to be caused by the cable pushing the rotor against its stop, until the stop fails and the rotor pushes into the disc - this would be a significant improvement.  The whole casting is new, with integral slots for the bumpers, rather than the screw or riveted on steel frame of the previous model.  Note that the worm gear for the odometer drive is present on this tach rotor, probably to simplify the parts list.  This is a second just as out of focus shot of the top retainer plate and rivets.

These rivets will have to be drilled out for disassembly, and replace with new.
The hairspring mounting is also different, retained here with a blob of adhesive rather that the clip arrangement used previously.

This is the rotor retainer plate.  A much more robust arrangement than the previous.  What you can't see in this is that the retainer plate comes in from one side, with a cutout around a slot between the odometer worm drive and the magnet rotor.  The rivets are swaged from the bottom as in the next shot-
 
 
 
 
 
 
 
 
 
 

The last case I assembled, I drilled a hole in the bottom in line with the adjuster.  Although I can set them pretty close with the drill set up, you never know, and I would hate to take the bezel off just to tweak it a little.