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There is a design difference between the after-1986 model glove compartment and the earlier model.
Notice how the forward left corner has a notch, in the part on the right, as shown in the above picture. This provides some additional room for the wiring harness that leads to the fuel injection computer.
1984-1986 (plus some of the early 1987) 325 and 325e models use Motronic 1.0 which has a 35-pin fuel injection computer. 1987 325i and later models use Motronic 1.1 or 1.3 which has a 55-pin fuel injection computer, hence more wires run to it. This is why the later models have a thicker wiring harness, and as such need more space … hence the notch in the glove compartment so as to provide this additional space.
The BMW part number for the BOTH bins are cast into the plastic mold, and is 51 16-18884243. The notch is simply cut out.
The later-design bin, with the notch, will work on earlier cars. The earlier-design bin, without the notch, should probably not be used on later cars or the fuel injection wiring harness will chafe.