[R-390] LPF-1 i.d.

[Dan Merz]

Hi,  this question may be related to 390a but I think it's more likely related to some other military radio. At a swapmeet,   I picked up what I thought was a small enclosed transformer with 4 posts marked grnd, 500,  15K, and 100K on the terminals and marked LPF-1  (low pass filter??),   about the size of an audio output transformer in the 390a.  I thought it might work well for 100K to 500 ohm impedance match for a crystal set to sound powered phones - which it did using the 15k, 500 and ground connections with the ground in common.  And it worked better than some of the  transformers recommended for this use that I picked up at Fair.  But it's not a transformer - more like an autoformer with only one leg (continuity dc-wise between the four posts) or a leg with two branches to the 15K and 100K posts.  It's a bit of a mystery but works well for what I wanted.  It didn't match anything I see in an RAL-8 or the 390a.  Has anyone run across this or know what it came out of.  I suspect it's part of an audio filter.   There are no other numbers or i.d. on it - it's black with 6 screw holes on the bottom flange.

There were only a few boatanchors at the swapmeet in Seattle, which was an antique radio club event.  I did see a couple of Hamm.  HQ-129's,  one for $50,  which surprisingly I think went unsold,  and one SX-28.  No sign of 390's.     

 thanks for any help,  on or off the list,  Dan