I have a few mechanical IF-filters from Collins Radio for sale which were designed to be used with an IF of 500kHz:
The first type is F500 Z 11 LSB (526-9419-000), new/unsoldered: 40,-USD ---
The second one is without type print, just with Collins type number: (526-9412-000), as far as I have found out this is a F500Z-6 mit B=2,95kHz, new/unsoldeted: 40,-USD ---
Finally I have this set of used filters for AM, LSB und USB: F500 Z 10 USB (526-9420-010), F500 Y 70 AM (526-9421-010), F500 Z 11 LSB (526-9410-010), these come including their matching transformers named BTC-12367 (6 ea) taken from the original installation. I want 80,-USD for this set. ---
All prices plus shipping from DL which is 8,-USD for registered shipping. I offer to use PayPal for payment.
If you are interested, please take a closer look at the picture but do not hesitate to ask if you have any question.
P.S.: Just for the case you have an "MSC Smart Filter" switched capacitor audio filter in your shack which you do not use anymore, I would consider a trade deal for the whole bunch of the mentioned IF-filters.