Hi Mark,
I also have two after-market filters that mostly have unintelligible writing on them. I <think> one of them is an Inrad/FoxTango (Blue lettering/sticker) 250Hz CW and the other might be a Wilson 6KHz AM with the correct center frequency. At least that's what the person I purchased it from told me. At some point I will sweep them on the spectrum analyzer and see how they look. But it's not a high priority for me right now. I don't run across filters for 301's very often. It's been my experience that CW filters are more available than AM filters. Comparatively speaking I don't think there were that many 301's sold and even fewer filters for them. No one really can really charge very much for them because the radios themselves aren't worth that much..
The rigs (that I am aware of) that used these same filter's (center frequency) were DZ-Kit's original Sienna rig - and they stopped offering the optional filters for sale about the same time that Inrad discontinued them (which was a looong time ago), the Yaesu FT-7b, R-530 (old Galaxy receiver??). So if anyone ever runs across any of these rigs, take a peek inside - you might find gold (in dem der hills).
Dayton/Xenia is next month - anyone going? One can usually find something they are looking for, but you might have to pay more than you want.
