DOWN TO MY LAST ONES! SOLD OVER 50, these have been very popular! It seems they have gone in a wide variety of radios with ease however they have nvere reported back! So it seems with no problems. 

 These are the new style flat "torsional" type mechanical filters (not the old "disk & wire" loaf of bread) made by Rockwell-Collins, same great specs, more modern design. These are all 455 KHz center frequency and are symmetrical (CW) style filters, 2K ohms& 30 pF load. I have on this listing 500 Hz narrow bandwidth for CW filters. The model numbers are 526-8610-020 for the 500 Hz . You are buying one filter at a time!!    These are all new old stock from Watkins Johnson and were used in receivers like the WJ-8700, etc. I will ship in a box with the filter wrapped up carefully. Have fun!

NOTE: I have been asked about the mechanical outline: I measured this and found the unit is approx. (inches) 2.09 long x .73 wide by .35 thick, with pins distance 1.7 inches, pin dia. approx .035.  Appears to be Collins type "LP".