Collins mech filter help - numbers

[N5AIT Allan Stephens]

Gang,

     Got a very nice 75A-3 on a swap a few weeks ago and am
still looking for a second narrow bw mechanical filter.  I
have learned that there are all sorts of Collins mecahnical
filters out there... just need one to fit the 75A-3.  One
set of numbers should be F455 B something-or-other, with last
number indicating bandwidth, or so it seems.  Problem is
running into the Collins parts numbers without any cross-reference
from Collins part numbers to the filter that would fit.

     So far have figured that Collins part number 526 xxxx xxx
is a mechanical filter, and the last three indicating (I think)
the filter bandwidth.  What I need is the Collins part number
for filters that will fit the 75A-3 (looking for narrow - CW -
filter).  How does a 526-9764-020 pan out? right IF (455) and
bw (200 cps) (I think) - but would it fit?

     Or if someone has one they want to part with....

     TIA,

   73,  Al  N5AIT
 modsteph at acs.eku.edu