My B600 was the same way when I got it, as its previous owner had opted to remove the front cover for some reason. Of course, the 600-series had moved the Wavemagnet out from the front cover, so this wasn't a huge impediment to operation. I did eventually get a replacement front cover (from a parted-out A600) which was a bit of a pain to install due to the cramped space near where it screws in, but straightforward otherwise. Here's a lousy photo of my B600 in this condition:
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Stereo: Pioneer SPEC-4, Pioneer SPEC-1, Kenwood KT-7500, Dual 1219, Nakamichi BX-100, Pioneer PD-M60, Paradigm Studio Monitors