I've got a few of them. First of all, I've got:

450kHz CF @6kHz bandwidth Z=20k
These units were used in the Collins 674/U, and later versions of the 651S-1
after the 2nd I.F. was switched.
75 dollars each, plus shipping........new old stock

455kHz USB/LSB pair.
I believe that this is the filter set for the Racal 6790 series
100 dollars for the pair, plus shipping

455kHz CF @ 6kHz bandwidth Z= 50 Ohms
These were special units for Collins Radio equipment. Good for that single
conversion receiver project
75 dollars each, plus shipping

Pete