"Reading this just makes me feel old cause I remember when the R-390A was the Navy's premier state-of-the-art SSB receiver, and that was in the SIXTIES!!!"
If being an R-390A user makes you feel old, having been a member of design team of the T-368 transmitter that accompanied the R-390A in the Army's GRC TTY communications vans, then I must be ANCIENT! ! ! ! !
Actually, the R-390A is still a very competitive receiver commanding very high prices on eBay, perhaps second only to the Collins 75A4 (whose design is heavy based on certain sections of the R-390A). At the time (circa 1960) many firms tried to duplicate the R-390A's variable frequency local oscillator but failed because no one could figure out a production alignment methodology that would produce the same frequency linearity as did the Collins produced LO unit. (At least at B&W we couldn't.) This involved the precise bending of a capacitive loading finger strip that paralleled a rotating, variable inductance coil and compensated for a small amount of tracking error in the coil's windings.
The old 'boat anchor' receivers still hold an advantage over most of the current generation of solid state units -- That is, when they break you can fix them yourself! :-)
IIRC, two versions of the R-390A were produced, one with a conventional tuning dial and the other with a geneva mechanism type counter showing the tuning setting but not the frequency. The receivers were produced by a number of firms, but so far as I know all of the LOs in them were manufactured by Collins Radio.