That is 49.4cm x 21.5cm x 6.6cm. Not an annoyingly big cover but definitely not to be called compact either
Turns out that the cover
sits perfectly on top of my new IBM Model M (49.0cm x 21.0cm x 4.5cm), basically covering the entire top face —including the top face edges— of the keeb and protecting it against dust and light:
The matching dimensions are absolute coincidence. Perfect width, left side:

Same perfect width on the right side, of course. Funny how in the pic the cover looks like having a prismatic geometry:

Perfect length, too. Really, what a coincidence. Also, as you can tell, in the afternoon sun rays would hit the board:

My copy is a
most recent manufactured blue label unit 6127, made
1999 in the UK by IBM UK (not Lexmark UK or Lexmark USA), and it does not suffer from the
warped upper case half problem which resulted in a visible black gap on Rhinofeed's
expensively refurbished unit and on
Modern Classic's 2017 unit:

As we could see, the cover does not cover the four side faces of the keeb but leaves them still exposed to sun light, dust and splashes of milk from muesli. Oh well. A hard plastic cover covering the entire keeb by sitting on the desktop would be humongous for the IBM Model M and probably fill the entire desk space, no thanks anyway!
If anyone's wondering, my unit has a German ISO layout and its space bar
does not produce any rattling sound during typing (e.g. during type-racing or normal typing), not even the faintest:
While taking the above photos of my new (and first Model M ever!) keeb, i noticed select spots which were slightly dirty. So now i am off to cleaning the spots with ethanol and vinegar-based cleaner. Last night i ordered a 5.5mm nut driver from Aliexpress for 1.44US$ and i will be posting more about my unit in some other thread.
I believe i got a very lucky deal on this unit…
