Oscillator, Radio Frequency (RF. 3/5A/449 MHz)

Michael O'Beirne

While looking for other things here I found the above oscillator module.  I’m looking for any info there may be.  My researches so far have not dug up anything.
The NSN is 5820-99-953-7433.  The manufacturer is EMI.  The manufacture date is “XC”, which appears to be 1966, March.
It’s the rough size of a Racal-Dana 9442 5MHz standard – ie 2” x 2” x 2.5” but is made of gilded brass and very heavy for the size.  Underneath is a recessed Cannon connector with its original plastic cap still in place.  This connector is a DB15 but has only 5 pins and a mini coax socket on either side of the pins.  It has three inspection stamps on one side.  On top is a big red label with green print: “RF 3/5 A”.
The external mechanical engineering is excellent; part has been milled out of a solid block of brass and all the six surfaces are gilded. The label says either 44.9MHz or 449MHz, both of which seem pretty unusual.
It may well be of no use to man or beast but I’d like to know a bit more about it please.  I have not yet opened it up for fear of damaging anything.  It will make a nice desk paperweight if nothing else.