Raytheon  RK 5609
Raytheon  RK-5609 shown next to a type 27 for size comparison
Raytheon tag with type number and serial number
The RK-5609 is a rare bird:  a very early (possibly first) device for the 2450-MHz  RF-heating band.  It has very expensive radar-like construction, vastly more costly than today's microwave-oven magnetrons, which put out typically ten times the power on the same frequency.
Amperex (Philips' U. S. agent) and Valvo
(a German Philips company) also sold it, so we don't know whether Raytheon or Philips did the development. 
(This was NOT the tube in Raytheon's early Radarange.)

Lud Sibley

The data below was supplied by Danial Stocks.

Some spec on the 5609 - was [I think] based on the design of the QK59 series of radar jammer magnetrons from WWII - these look essentially identical except for a tuner gear on top. in which case it has a 12 vane type anode
Spec Heater 6.3V 3.8A [Tubelore quotes a different H current, but is a typo.
Have tested a 5609 personally and can confirm 3.8A is correct] f 2425 - 2475MHz typically 1.5 kV 150ma have seen slightly different figures from other data sources but this is essentially correct o/p 70 - 125W [cant say
where the o/p lies, this is the range of figs Ive seen for it. The cathode needs some forced air cooling - hence the heatsink fins in the socket. May have to reduce the heater voltage during opn. dont know..