Hi,
Today I received a small packet with an MMC20CL cartridge, as a complete red box with all its accessories (yes, even the brush), the nice Brüel & Kjær graph and instructions. It is dated February 1979. Surely one of the first produced. The number at the back of the cartridge matches the other stickers' numbers: 3204. My review in the Revue du Son is from September 1980.
What is surprising—I was actually buying a box with accessories—is the fact that it actually plays quite well. Not a trace of dirt at the tip. It even tracks better than my SMMC20EN (ex: the kids' choir in Another Brick when they shout, alway been a tough one!). Its treble is much sweeter than that of the Soundsmith, very delicate even, not dull. Piano sounds fantastic!
How long will it last? Could it be that it was repaired by B&O themselves? Did they repair your cartridge at all?
Anyway, for £30 the risk was low, and you can count me as one of the CL adorers!
Edit: It doesn't look like the one on Peter's pictures, the tip seems to be glued to the sapphire rod. Sorry I don't have a microscope!