[Collins] Collins R-391, 51J4

[Tom Chirhart]

Hello all. I just found an R-391 and a 51J4 locally and could use some
advice/help.
If there is a 391 expert out there I'd appreciate an email. I do need one
lock nut for the Kilocycle Change knob and a pair of knobs for the Local
Gain and RF Gain, I think the R-390 or 390A knobs are compatible. Also is
there a manual available via the web anywhere?  I could not find one during
a search. Any idea if the 391 was mass produced? I don't recall seeing them
in the Navy or Coast Guard.
51J4
I am looking for the plug in mechanical filters for the 51J4, this unit came
with one filter, it's not in any of the filter lists out on the web, it's
nomenclature is F500 B-18 Part Number 522 9100 002. In addition I also need
a replacement skirt for the Band Change knob, or two new ones if someone has
any.
There was a plate on the 51J4 at one time, long gone, but has a stamped
number 2167 where it was mounted. Would this indicate the serial number of
the unit? Does someone make these plates? I seem to have seen that someone
does. The rear of the chassis has MFP stamped on it. I recall some mention
of a Fungus Protection stamp?
What limited info I can find on the 391 indicates they were used for
non-standard purposes. A local retired USAF neighbor states he remembers
them used for Air/Ground operations in remote applications...
Please reply direct to save bandwidth.
Thanks
73 Tom K4NCG