It appears to be the rear blower that RealOEM shows listed for my X5 (and others). Apparently it's under the console, though I'm not sure. Since I haven't seen it in person, I've no idea what the screw is for.

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01 BMW X5 E53 3.0i, 5L40E, 7/13/01
topas-blau, Leder-Montana grau

Here:
14 Lexus ES350 3.5L, U660E
09 HHR Panel 2.2L, 4T45E
04 Chevy 2500HD 6.0L, 4L80E
98 GMC Sierra 1500 5.7L, 4L60E

Gone:
66 Chevelle Malibu 2dr, 327>427c.i., TH350>PGlide/transbrake
08 Cobalt Coupe 2.2L, 4T45E
69 & 75 C10s, 350c.i., TH350
86 S10, 2.8l V6, 700R4
73 Volvo 142 2.0l, man4
73 VW SuperBeetle 1.6l, man4
64 VW 1.2l, man.4
67 Dodge Monaco 500 2dr, 383 c.i., A727
56 Chevy 210 4dr, 265 c.i., PG