I was made aware there are two types because when I ordered new drive belts from Martin he sent me this link to distinguish the type:

The difference shown in the picture applies to the Beocord 4500. But does it apply to the Beocenter 9500 just as well? Kai

You would need to check with Martin - but the picture was sent to me after I specifically asked about BC9500 drive belts.  Mine has the two screws next to the tape head so is clearly the older version.

And of course the BC9500 is more or less a Beosystem 4500 in one cabinet.

Again the archived forum is difficult to search, but this may also be useful: /forum/imported-unmapped/using-a-raspberry-pi-as-a-diy-equivalent-to-logitech-harmony#post-2168657

The difference is that the earlier model uses three motors and the later one just one. The deck from the BC2500 is used. Both perfectly ok.

Thanks very much. My deck seems to be identical to the one in the Beocord 7000. It's apparently the later version. Any sonical differences? What about the deck in the 9300? Again a different mechanism? Kai

The BC9300 was basically a BC2500 in 'new' packaging.  Hence, compared to the 9500, the tape deck lost Dolby B/C and their automatic selection, as well as auto or manual level control, and the microphone amplifier.