I picked up a bunch of old ham gear and parts at a recent estate sale
about a week ago. One item that I've not been able to find a part number
for is a Collins Mechanical Filter, still in the factory box. The box
and the filter have the numbers 526 9448 00 shown, and the filter also
says F 455 FB 21 8V2. There's also a sticker on one side of the filter
that has a hand written two-line note on it, it appears to say:
200.8 HI 45629 K.C, 200.8 LO 453.62 K.C (both "200.8" notations actually
appear to be "20D.8".)

Does anyone know what particular receiver this filter is meant to be
used in, and what selectivity value it is?

Thanks,
Larry